Heat engine

ABSTRACT

An apparatus has a heat engine and a power output member drivenly connected to the piston of the heat engine and having an output for supplying work. The displacer is driven by an adjustable drive member. An adjustable signal generator is provided for modulating a signal which is sent to the adjustable drive to adjust the cycle profile of the displacer. The phase angle, the dwell time of the displacer at one or both ends of its cycle and/or the velocity of the displacer is thus adjusted.

This application is a continuation-in-part of application Ser. No.09/523,142 filed Mar. 10, 2000.

This application claims the benefit of U.S. Provisional Application No.60/182,106, filed Feb. 11, 2000, U.S. Provisional Application Ser. No.60/182,105, filed Feb. 11, 2000, and U.S. Provisional Application No.60/182,050, filed Feb. 11, 2000.

FIELD OF THE INVENTION

This invention relates to a heat engine.

BACKGROUND OF THE INVENTION

The heat engine is an alternate engine to the internal combustionengine. Various designs for heat engines have been developed in thepast. Despite its potential for greater thermodynamic efficiencycompared to internal combustion engines, heat engines have been used inonly limited applications in the past due to several factors includingthe complexity of the designs, the weight of the engine per unit ofhorse power output as well as the difficulty in starting a heat engine.

SUMMARY OF THE INVENTION

In accordance with the instant invention, an improved design for a heatengine is disclosed. In one embodiment, the heat engine is made fromlightweight sheet metal. By using a plurality of cylindrical containers,one nested inside the other for the displacer, the combustion andcooling chambers as well as to create an air flow path between theheating and cooling chambers, a rugged durable lightweight constructionis achieved.

In another embodiment, the heat engine utilizes a power piston which isbiased to a first position. By biasing the piston, several advantagesare obtained. First, the heat engine may be self starting provided thepower piston is biased so as to be initially positioned in the coolingchamber. A further advantage is that by using an electrical means (eg. asolenoid, an electromagnet or the like) and preferably a magnetic drivemember (eg. an electromagnet) to move the displacer, preferably inresponse to the position of the power piston, a complicated mechanicallinkage between the power piston and the displacer is not required thussimplifying the design. Further, by using an electrical linkage, thephase angle between the displacer and the power piston may be adjusted.

The heat engine of the instant invention may be combined with a fuelsource (eg. butane), a linear generator and an electrically operatedlight emitting means to create a flashlight or other portable lightsource. It will be appreciated that due to the simplicity of the designof the instant invention, the heat engine as well as the lineargenerator are each adapted to be scaled up or down so as to producegreater or lessor amounts of power. Accordingly, in another embodiment,the heat engine together with a linear generator and a fuel source maybe used as a generator. It will further be appreciated that byconnecting a linear generator to a source of electricity (eg. standardelectrical outlet) the electricity from a power grid may be used to runthe linear generator as a motor whereby the power piston effectivelydrives the displacer. In such a case, the heat engine may be used as arefrigerator or a cryogenic cooler. In such an embodiment, the heatingand cooling chambers of the heat engine are effectively reversed and nocombustion chamber is required.

In accordance with one aspect of the instant invention, there isprovided an apparatus comprising:

(a) a heat engine comprising:

(i) a container defining a sealed region within which a working fluid iscirculated when the heat engine is in use, the sealed region having aheating chamber and a cooling chamber, the heating and cooling chambersbeing in fluid flow communication via a working fluid passageway;

(ii) a variable heat source thermally connected to the heating chamberwhereby the variable heat source provides variable heat levels to theworking fluid;

(iii) a displacer movably mounted in the sealed region between a firstposition and a second position to define a displacer cycle profile;

(iv) a piston movably mounted in the sealed region between a firstposition and a second position to define a piston cycle profile, one ofthe displacer and the piston has an adjustable drive member associatedtherewith for moving the one of the displacer and the piston in responseto a signal and the other of the displacer and the piston is movable inthe sealed region due to forces applied thereto by the working fluid;

(b) a power output member drivenly connected to the piston and having anoutput for supplying work; and,

(c) an adjustable signal generator for modulating the signal provided tothe adjustable drive to adjust the cycle profile of the one of thedisplacer and the piston.

In one embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the piston comprises a portion ofthe electric generator and the displacer is driven by the adjustabledrive member.

In another embodiment, the adjustable signal generator comprises asignal modulator and the piston whereby the movement of the pistongenerates a signal that is sent to the signal modulator. Preferably, thepiston includes at least one magnet and the generator includes at leastone coil and the piston is mounted in the heat engine for movementrelative to the at least one coil and the movement of the at least onemagnet relative to the at least one coil produces the signal that issent to the adjustable signal generator.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the piston moves at a phase anglewith respect to the displacer and the adjustable signal generatormodulates the signal provided to the adjustable drive member to alsoadjust the phase angle.

In another embodiment, the heat engine has a thermal efficiency thatvaries under varying load conditions and the adjustable signal generatoris responsive to power demand from the power output member to modulatethe signal sent to the adjustable drive member to maintain the thermalefficiency of the heat engine in a preset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the piston comprises a portion ofthe electric generator and the displacer is driven by the adjustabledrive member.

In another embodiment, the adjustable signal generator comprises asignal modulator and the piston whereby the movement of the pistongenerates a signal that is sent to the signal modulator.

In another embodiment, the piston includes at least one magnet and thegenerator includes at least one coil and the piston is mounted in theheat engine for movement relative to the at least one coil and themovement of the at least one magnet relative to the at least one coilproduces the signal that is sent to the signal modulator.

In another embodiment, the displacer moves between a first positionadjacent the variable heat source and a second position distal to thevariable heat source and has a dwell time in each of the first andsecond positions, and the cycle profile describes the velocity of thedisplacer as it moves between the first and second positions and thedwell time of the displacer when it is in each of the first and secondpositions, and the adjustable signal generator modulates the signalprovided to the adjustable drive member to adjust at least one of thevelocity of the displacer, the dwell time of the displacer when in thefirst position and the dwell time of the displacer when in the secondposition.

In another embodiment, the sealed region has a cooling chamber for theworking fluid and the piston moves between a first position wherein itis positioned in the cooling region and a second position wherein it ispositioned out of the cooling chamber and has a dwell time in each ofthe first and second positions, and the cycle profile describes thevelocity of the piston as it moves between the first and secondpositions and the dwell time of the piston when it is in each of thefirst and second positions, and the adjustable signal generatormodulates the signal provided to the adjustable drive member to adjustat least one of the velocity of the piston, the dwell time of the pistonwhen in the first position and the dwell time of the piston when in thesecond position.

In another embodiment, the adjustable signal generator has a manualadjustment control.

In another embodiment, the heat engine has a thermal efficiency thatvaries under varying load conditions and the adjustable signal generatoris responsive to power demand from the power output member to modulatethe signal sent to the adjustable drive member to maintain the thermalefficiency of the heat engine in a preset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the heat engine has a thermalefficiency that varies under varying load conditions and the adjustablesignal generator is responsive to power demand from the output tomodulate the signal sent to the adjustable drive member to maintain thethermal efficiency of the heat engine in a preset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the piston comprises a portion ofthe electric generator.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the apparatus further comprises afeedback member responsive to power demand from the electric generatorby the load to modulate the amount of heat provided by the heat sourceto the working fluid.

In another embodiment, the feedback member includes a thermal sensorthermally connected to a thermal source whose temperature changes as thepower demand from the output varies.

In another embodiment, the thermal sensor is reconfigurable on heatingand is mechanically connected to the variable heat source to adjust theamount of heat provided by the variable heat source in response to areconfiguration of the thermal sensor.

In another embodiment, the thermal source is the heat source whereby thetemperature of the heat source is used to sense the power demand appliedto the output.

In another embodiment, the feedback member further comprises an internalload member which draws current from the output. In another embodiment,the feedback member comprises a circuit including a resistorelectrically connected to the circuit to draw current proportional tothe power demand drawn from the output and the thermal source is theresistor whereby the temperature of the resistor is used to sense thepower demand from the output.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source has acontrol member to adjust the temperature of the variable heat source anda feedback member is drivingly connected to the control member andcomprises a circuit including a sensor portion which provides a signalto the control member based on the power demand drawn from the output.

In another embodiment, the sensor portion provides an electrical signalto the control member causing the variable heat source to adjust theamount of heat provided to the working fluid in response to the signalfrom the sensor portion.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member is drivingly connected to the variable fuel flow valveand includes a thermal sensor thermally connected to the combustionchamber whereby the temperature of the combustion chamber variesinversely to the power drawn from the linear generator by the load, thethermal sensor senses the temperature of the combustion chamber and thefeedback member adjusts the flow rate of fuel supplied to the combustionchamber to maintain the temperature of the combustion chamber within apreset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member is drivingly connected to the variable fuel flow valveand comprises a circuit including a resistor electrically connected tothe circuit to draw current proportional to the power demand drawn fromthe output, and a thermal sensor thermally connected to the resistorwhereby the thermal sensor indirectly senses the power demand of a loadapplied to the output and the feedback member adjusts the flow rate offuel supplied to the combustion chamber to maintain the temperature ofthe combustion chamber within a preset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member is drivingly connected to the variable fuel flow valveand comprises a circuit including an internal load member which drawscurrent from the output and a resistor electrically connected to thecircuit to draw current relative to the power demand drawn from theoutput, and a thermal sensor is thermally connected to the resistorwhereby the thermal sensor indirectly senses the power demand of theload and the internal load and the feedback member adjusts the flow rateof fuel supplied to the combustion chamber to maintain the temperatureof the combustion chamber within a preset range.

In another embodiment, the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member comprises a controller operatively connected to thevariable fuel flow valve and a current sensor connected to the outputwhereby the current sensor senses the current drawn from the output andthe controller adjusts the flow rate of fuel supplied to the combustionchamber based on the amount of current drawn from the load.

In another embodiment, the variable fuel flow valve comprises aplurality of valves each of which is independently operable by thecontroller.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to explain moreclearly how it may be carried into effect, reference will now be made byway of example to the accompanying drawings which show preferredembodiments of the present invention, in which:

FIG. 1 is a partially cut away perspective view of a heat engineaccording to the instant invention;

FIG. 2a is a cross section along the line 2—2 of FIG. 1 of a heat engineconfigured as a flashlight with the heat exchanger for the fresh air forcombustion removed, with the displacer positioned adjacent the heatercup and the power piston positioned at the end of the power stroke;

FIG. 2b is a cross section along the line 2—2 of FIG. 1 configured as aflashlight with the heat exchanger for the fresh air for combustionremoved, with the displacer positioned distal to the heater cup and thepower piston positioned at the beginning of the power stroke;

FIG. 2c is a cross section along the line 2—2 of FIG. 1 of an alternateembodiment with the displacer positioned adjacent the heater cup and thepower piston positioned at the end of the power stroke;

FIG. 2d is a cross section along the line 2—2 of FIG. 1 of an alternateembodiment with the displacer positioned distal to the heater cup andthe power piston positioned at the beginning of the power stroke;

FIG. 2e is a cross section along the line 2—2 of FIG. 1 of a furtheralternate embodiment configured as a flashlight with the displacerpositioned adjacent the heater cup and the power piston positioned atthe end of the power stroke;

FIG. 3 is an enlargement of the heating and regeneration zones of thecross section of FIG. 2c;

FIG. 4 is an enlargement of the cooling zone and linear generator ofFIG. 2c;

FIG. 5 is an exploded view of the displacer and electromagnet of FIG. 2;

FIG. 6a is a perspective view of the heat exchanger for the heating zoneand the regeneration zone;

FIG. 6b is a perspective view of the air flow through an alternateversion of the heat exchanger for the heating zone;

FIG. 6c is an cross section along the line 6—6 in FIG. 6b showing theair flow through the heat exchanger for the heating zone of FIG. 6b;

FIG. 6d is an enlargement showing the air flow through the heatexchanger for the regeneration zone of FIG. 6a;

FIG. 7 is a perspective view of the working components of FIG. 2a withthe inner and outer cylinders removed;

FIG. 8 is a schematic drawing of the control circuit for theelectromagnet of FIG. 5;

FIG. 9 is a partially cut away perspective view of a heat engineaccording to a second embodiment of the instant invention which employsa magnetic drive system wherein the electronic control shown in FIGS. 9and 10 has been removed;

FIG. 10 is a cross section along the line 10—10 of FIG. 9 with the heatexchanger for the fresh air for combustion removed, with the displacerpositioned adjacent the heater cup and the power piston positioned atthe end of the power stroke;

FIG. 11 is a cross section along the line 10—10 of FIG. 9 with the heatexchanger for the fresh air for combustion removed, with the displacerpositioned distal to the heater cup and the power piston positioned atthe beginning of the power stroke;

FIG. 12 is a perspective view of a louvred fin;

FIG. 12a is a perspective view of another louvred fin;

FIG. 12b is a cross section of a cylindrical tube with the louvred finof FIG. 12a attached thereto;

FIG. 12c is a perspective view of an alternate louvred fin;

FIG. 12d is a perspective view of an alternate louvred fin;

FIG. 12e is a perspective view of a portion of a heat exchanger withlouvred fins and cyclonic flow in the circulating fluid as the fluidtravels axially through the heat exchanger;

FIG. 12f is a perspective view of a portion of a heat exchanger withlouvred fins and cross flow in the circulating fluid as the fluidtravels axially through the heat exchanger;

FIG. 13 is a perspective view of a radial blade;

FIG. 14 is a perspective view of a further embodiment of a spacer ring;

FIG. 15 is a perspective view of a further embodiment of a spacer ring;

FIG. 16 is a perspective view of a helical fin;

FIG. 17 is an enlarged view of the helical fin of FIG. 16 with analternate louvre;

FIG. 18a is an enlarged perspective view of a louvre of the helical finof FIG. 16 showing the sublouvres;

FIG. 18b is an enlarged perspective view of a louvre of the helical finof FIG. 16 showing alternate sublouvres;

FIG. 19 is a cross section along the line 11—11 of FIG. 11a of a furtheralternate embodiment of the heat engine;

FIG. 20 is a cross section along the line 11—11 of FIG. 11a of a furtheralternate embodiment of the heat engine;

FIG. 21 is an assembly for a power piston or a displacer wherein thepower piston of displacer is constructed from two containers that arewelded together;

FIG. 22 is an assembly for a power piston or a displacer wherein thepower piston of displacer is constructed from two containers that arethreadedly engaged;

FIG. 23 is an assembly for a power piston or a displacer wherein thepower piston of displacer is constructed from a first and secondcontainers wherein the second container is press fitted into the openingof the first container; and, FIGS. 24a and b are graphs of the movementof the power piston compared to the movement of the displacer in oneembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

The heat engine described herein contains several novel designinnovations including the construction of the heat engine from sheetmetal or the like, the construction and positioning of the heatexchangers (including the regenerator), the drive system for thedisplacer and the power piston so as to allow different cycles for thedisplacer and the power piston, the feedback system for controlling theamount of heat (energy) provided to the working fluid and the ability tosynchronize the frequency of several generators to allow their series orparallel connection to a load.

In the preferred embodiments of FIGS. 1-4, 7, 9-11, 19 and 20 the heatengine includes a linear generator as the power output member. It willbe appreciated that the heat engine may be drivingly connected to anyother electric generator known in the art. In an alternate preferredembodiment, the heat engine includes a mechanical linear to rotaryconverter which are known in the art as the power output member. It willbe appreciated that the design innovations of this disclosure may beused with either any power output member known in the art. Thus thepiston may be linked by any means known in the art, eg., to providelinear or rotary mechanical power. Accordingly, similar parts have beenreferred to by the same reference numeral in all embodiments.

In accordance with the embodiments of FIGS. 2a, 2 b, 2 e and 7, a lightbulb is incorporated into the housing of the heat engine and so as toprovide a portable flashlight. The heat engine is drivingly connected toa linear generator which is used to create current to power one or moreincandescent light bulbs, fluorescent light bulbs, LEDs, gas plasmadischarge light sources or the like. It will be appreciated that theheat engine may be powered by any heat source known in the art. In apreferred embodiment, the flashlight housing includes a fuel reservoirwhich, upon combustion, provides heat to power the heat engine.Accordingly, the flashlight comprises four main components namely a heatsource, a heat engine, a linear generator and a light emitting device(eg. a light bulb). It will also be appreciated that the lineargenerator may be used to provide power for any required purpose and thatthe heat engine and the linear generator may be configured as anelectric generator or may be connectable to an electric motor or anyother application that requires electricity (i.e. the load). In any suchapplication, the component to which the linear generator provideselectricity may be housed with the heat engine and the linear generatorof the may be a separate discrete component.

As shown in the drawings attached hereto, the components are shown setout in a linear array (i.e. they are positioned sequentially alonglongitudinal axis A of the flashlight). However, it will be appreciatedthat the components may be set up in various configurations. Forexample, the fuel reservoir need not be positioned directly in line withthe heat engine. Similarly, the light bulb or other powered componentneed not be positioned along longitudinal axis A of the flashlight butmay be positioned at any desired point by adjusting the shape of theouter housing and providing a sufficient length of wire to connect thelight bulb or other powered component to the linear generator.Alternately, the housing of the heat engine and the linear generator mayhave an electrical outlet for receiving a standard electric plug.

The following description is based on the flashlight model which has asingle light bulb. However, the device, complete with an on board heatsource (eg. a reservoir filled with a combustible fuel and a combustionchamber), creates a self contained, light weight light source which maybe in the form of a flash light, a portable camping light, a lamp or thelike. In this application, the flashlight has been described as if itwere standing vertically on a table with bulb 48 positioned at thebottom. References to upper and lower, vertical or horizontal in thisapplication are for reasons of convenience based upon this orientationof the flashlight in the drawings. It will be appreciated that the heatengine and the linear generator may be used when the housing of theapparatus is in any particular orientation.

Thin Walled Construction

According to one aspect of the instant invention, a novel constructionof a heat engine is provided which uses thin walled structures to housethe working or moving components of the heat engine (i.e. displacer 46and power piston 50) within a working container having first and secondends. The working fluid is circulated between the first end of theworking container which is warmer than the second end. In contrast toearlier designs wherein the working container is prepared from a blockof metal which is machined to produce a space within which the workingfluid circulates or which is forged, this design uses sheet metal andthe like to form a container. Positioning members are provided todimensionally stabilize the walls of the container thereby providing adurable structure. Due to the construction materials used, the heatengine is light weight and has good thermal efficiency since the thinwalled construction allows for faster heat transfer to and from theworking fluid and significantly reduced heat retention by the componentsof the heat engine.

In a more preferred embodiment, the working container is an innercontainer which is housed within an outer housing and the positioningmembers extend between the outer housing and the working container at aplurality of locations along the length of the working container. Thepositioning members may be provided only at the longitudinally opposedends of the inner container. For example, the positioning means may beaffixed to the opposed ends of the inner and/or outer containers andextend generally parallel to the longitudinal axis of the heat engine todraw the opposed ends together (eg. a bolt and a butterfly nut), inwhich case they function as clamping means to draw the opposed endstogether and seal the inner cavity. Preferably, the positioning meansextends generally transverse to the longitudinal axis of the heatengine. In such a case, if the passageway through which the workingfluid travels between the first and second ends of the inner containeris positioned in the space between the outer housing and the innercontainer, then the positioning members are configured to allow fluidflow there through. The positioning members may also function as heatexchangers and/or a regenerator thereby reducing the number ofcomponents required for constructing a heat engine. More preferably, theouter housing is also of a thin walled construction.

As in the embodiment of FIG. 1, the container may be open topped whereinthe combustion chamber is positioned at least partially within andpreferably wholly within the inner container and is used todimensionally stabilize the top of the inner container. The combustionchamber is constructed from materials which will maintain theirstructural integrity at combustion temperatures and therefore, thecombustion chamber may be prepared by standard construction techniquesfor turbine engine components (eg. stamping components out of a supernickel alloy to maximize heat transfer by minimizing the wallthickness).

FIGS. 1, 2 a, 9-11, 19 and 20 exemplify this construction. Referring toFIG. 2a, a flashlight 10 is shown with each of the components set out ina longitudinally extending array inside outer wall 12. Outer wall 12 hasa first end 14 and a second end 16. A start or ignition button 18 isprovided, preferably on the longitudinally outer wall 12.

As shown in FIGS. 2a-2 d, flashlight 10 comprises a heating zone 22, aregeneration zone 24, a cooling zone 26 and an electrical generationzone 28. Flashlight 10 is provided with a housing to include thecomponents for each of these four zones. The housing comprises outerwall 12 and inner wall 30 which are preferably coaxially positionedabout longitudinal axis A (see FIG. 1). While the housing which is shownin the drawings comprises nested cylinders, it will be appreciated thatthe housing may comprise inner and outer containers that may be of anyshape and need not be coaxially mounted. Further, the housing may allowany configuration of the components provided the electrical generationmeans is drivenly connected to the heat engine.

Outer wall 12 has an outer surface 32 and an inner surface 34. Innerwall 30 has an outer surface 36 and an inner surface 38. Inner surface34 of outer wall 12 and outer surface 36 of inner wall 30 are spacedapart to define an outer cavity which may be used as annular fluid flowpath 40 within which regenerator 42 is preferably positioned. Theconstruction techniques of this design may be used in configurations ofheat engines that do not include a regenerator or which do not positionthe regenerator in an annular passageway exterior to the inner cavitywithin which the displacer is positioned.

In the preferred embodiment of FIGS. 2a and 2 b, positioned inside innerwall 30 are heater cup 44, displacer 46, driver 48 for moving displacer46, power piston 50 and the linear generator comprising a plurality ofmagnets 52, ferrite beads 54 and coils 56. Light bulb 58 is mounted atsecond end 16 of outer wall 12. Alternately, piston 50 may be a portionof the linear generator (see eg. FIG. 10).

As shown in FIG. 3, heater cup 44 has an inner surface 60 and an outersurface 62. Outer surface 62 is spaced from inner surface 38 of innerwall 30 so as to define a fluid flow path 64. Fluid flow path 64 is afirst passageway that is in fluid flow communication with fluid flowpath 40 by means of a plurality of spaced apart openings 66 which areprovided in inner wall 30. Accordingly, fluid flow path 64 and openings66 define a passageway connecting the interior of the upper portion ofinner wall 30 (i.e. heating chamber 160) with fluid flow path 40. In theembodiment of FIG. 1, inner wall 30 terminates prior to top 90 of heatercup 44 thereby providing an annular space 64 through which the upwardlyflowing working fluid passes as it travels from heating chamber 140 toannular fluid flow path 40. A plurality of positioning members todimensionally stabilize the end of inner wall 30 adjacent heater cup 44are provided in fluid flow paths 64 and 40. These positioning membersmay be in the form of rings that extend continuously around outersurface 62 and engage inner surface 38 of inner wall 30 to prevent innerwall from contracting inwardly when the heat engine is operating. Thesepositioning members may also be constructed to assist in the transfer ofheat to the working fluid. Examples of such positioning members areprotrusions 106 (see FIG. 3), contact with wall of burner cup 44 (seeFIG. 2a), spacer rings 164, 476 (see FIGS. 14 and 15), louvred fins 428,440, 468 (see FIGS. 12, 12 a, 12 c, 12 d and 13) and helical louvred fin448 (see FIG. 16). In another alternate embodiment, inner and outerwalls 30 and 12 may be two containers that are prepared by die stampingand then connected together at their open (top) ends by placing onecontainer inside the other and spin welding the top ends together toform a double walled vessel. The portions of the containers that arespun welded together define an intermediate portion and openings 66 maybe provided therein to allow heating chamber 140 to be in fluid flowcommunication with fluid flow path 40 (see eg. FIG. 3).

In the embodiment of FIGS. 2a and 2 b, inner wall 30 has a swedgedportion 204 at which point inner wall 30 has an increased diameterthereby bringing inner and outer walls 30 and 12 into engagement. Thismethod of assembly is advantageous if inner wall 30 is prepared from apreformed cylindrical tube.

This engagement, for example over the length of the electrical generatorzone 28, maintains the co-axial alignment of the cylinders. In theembodiment of FIG. 4, outer wall 12 has a uniform diameter along itslength and accordingly is maintained in a spaced apart relationship frominner wall 30 by, for example, a sealant which is inserted in gap 166below openings 158 or by spacer rings 164. As shown in FIG. 15, spacerrings 164 may be generally annular members having a generally U shapedprofile in cross section. As such, ring 164 has a pair of opposed edges262 extending from upper end 264 to trough portion 266 to define an openarea 268. Preferably, opposed edges 262 extend outwardly at a sufficientangle α to central axis B which extends through ring 164 so that upperends 264 are compressed towards each other when ring 164 is insertedbetween outer and inner walls 12 and 30 thus providing a tight slidingfit to mechanical lock the cylinders together. A plurality of rings 164which are spaced apart in gap 166 provides sufficient mechanicalconnection between outer and inner walls 12 and 30 so as to coaxiallyalign them.

As is exemplified by FIG. 1, providing any such positioning membersbetween spaced apart inner and outer walls creates a sandwichedconstruction wherein the inner and outer walls become mutually selfsupporting. By including a plurality of such spaced apart members,longitudinally spaced apart portions of, for example, outer wall 12 andinner wall 30 (e.g. positioned adjacent each of heater cup 44 and piston50), may be in contact with each other and transmit stresses (eitherinwardly directed or outwardly directed forces) between the inner walland the outer wall. By maintaining the relative position of the innerand outer walls, the positioning members allow the mechanical strengthof the inner and outer walls to be combined.

For example, in the embodiment of FIG. 1, at the lower end of the heatengine, a plurality of rings 164 are provided. At the upper end, innerwall 30 is dimensionally stabilized by louvred fins which are providedin both passageways 64 and 88 to thereby hold inner wall 30 and outerwall 12 at fixed positions with respect to heater cup 44.

In the embodiments of FIGS. 2a-2 d, a gap 166 exists between inner andouter walls 30 and 12 below the upper extent of travel of piston 50. Thegap between inner and outer walls 30 and 12 is sealed so as to cause theworking fluid to enter cooling chamber 160 and act on piston 50.Preferably, the gap is sealed immediately below openings 158 so as toprevent working fluid from entering gap 166 which would function as adead zone in the heat engine. This gap may be sealed in several ways.For example, one or more rings 164 may be provided to seal gap 166. Inan alternate embodiment, a sealant (eg. epoxy) may be applied to fillall or a portion of gap 166. In the alternate embodiment of FIG. 2e,inner wall 30 is swedged outwardly immediately below openings 158 suchthat inner and outer walls 30 and 12 are positioned adjacent each otherin the cooling zone. The positioning of inner and outer walls 30 and 12adjacent each other or the use of epoxy are additional examples ofpositioning members as they utilize the interplay between the inner andouter walls 30 and 12 to stabilize inner and outer walls 30 and 12.

In a preferred embodiment, inner wall 30 and outer wall 12 are each of a“thin walled” construction. For example, each of inner wall 30 and outerwall 12 may be made from a metal such as aluminum, stainless steel,super metal alloys and the like, and are preferably made from stainlesssteel and the like. The wall thickness of cylinders 12 and 30 may varyfrom about 0.001 to about 0.250 inches, preferably from about 0.005 toabout 0.125 inches, more preferably from about 0.01 to about 0.075inches and, most preferably from about 0.02 to about 0.05 inches.Similarly, the walls of displacer 46 as well as the walls of piston 50may be made from the same or similar materials. In larger heat engines(eg. those over 12 inches in diameter), the wall thickness is preferablyselected so as to be greater than one sixtieth of the diameter of innerwall 30 and preferably about one thirtieth of the diameter of inner wall30 when the wall is constructed for super nickel alloys and othersimilar materials whose strength is will not be significantlycompromised at 600° C.

Accordingly, the main components of the heat engine may be constructedfrom sheet metal or the like using the same materials and in a mannerthat is similar to the containers which are used for soft drink cans orthe like. In this preferred embodiment, inner and outer walls 30 and 12are formed from prefabricated components (prepared eg. by stamping ordrawing) which are then assembled together to form the heat engine. Forexample, inner and outer walls 30 and 12 may be prepared from sheetmetal by roll forming the sheet metal and then laser welding the sheetmetal to form a longitudinally extending tube. Alternately, metal may bedrawn through a die to form a cylindrical tube. Openings 66 and 158 ininner wall 30 may then be made by stamping, drilling, laser cutting orthe like. A circular bottom plate may be obtained from sheet metal bystamping and then roll formed or welded to the tube to produce an openedtop container into which the power piston and the displacer may beplaced. Alternately, a prefabricated open topped container may be formedby stamping metal using a high speed carbide die. This is in contrast toexisting techniques for forming engines wherein a block of metal is castand subsequently bored or the like to prepare the engine body thusresulting in an engine which is much heavier than is structurallyrequired for a heat engine.

Similarly, displacer 46 may be manufactured from roll formed sheet metalwhich is then laser welded together. Bottom 146 and top 136 may then beaffixed to the side walls by roll forming, welding, brazing, the use ofan adhesive or the like. Divider plates 144 may be added as required inthe manufacturing operation. Once sealed, displacer 46 provides a ruggedconstruction which will withstand the heat and stresses applied todisplacer 46 in the heat engine. A power piston may be constructed in asimilar fashion.

As shown in FIGS. 21-23, displacer 46 or power piston 50 may beconstructed from two open topped containers 498 which are joinedtogether, such as at the mid point of displacer 46 by welding along seamline 500. Each container comprises longitudinally extending side walls502 and an end wall 504. Side walls and end walls 502 and 504 may beintegrally formed such as by high speed carbide die stamping or,alternately, side walls 502 may be prepared by drawings metal through adie to form a preformed longitudinally extending cylindrical tube andend wall 504 may be affixed thereto by roll forming or the like. It willbe appreciate that welding seam 500 may be provided at any positionalong side walls 502. By providing end walls 504 to dimensionallystabilize the opposed ends of displacer 46, and by sealing side wallsand end walls 502 and 504 of displacer 46 so as to contain a sealedcavity 506, the overall exterior structure of displacer 46 issufficiently strong to act as a displacer (or a power piston) in a heatengine.

FIG. 22 shows an alternate embodiment wherein cap 508 is provided withwalls 510 which have a thread 512 provided on the inner surface thereof.The distal portion of walls 502 from end 504 are recessed inwardsslightly and have a mating thread 514 provided thereon. Accordingly,displacer 46 (or a power piston 50) may be constructed by providing anopen topped vessel and screwing a cap 508 thereon.

A further alternate construction is shown in FIG. 23. In this case, acap 516 is provided. Cap 516 has walls 518. Portion 520 of walls 518 arerecessed inward slightly so as to provide a seat for the distal end ofwalls 502 to be received thereon. The diameter of the outer surface ofwalls 520 is slightly larger than the diameter of the inner surface ofwalls 502 so that portions 520 lockingly engage the inner surface ofwalls 502. In this way, a sealed displacer 46 (or power piston 50) maybe provided. It will be appreciated that in the embodiments of FIGS. 22and 23, one opposed end of walls 502 is stabilized by end wall 504 andthe other opposed end of walls 502 is stabilized by cap 508, 518.

In order to reduce thermal transfers due to radiation and convectionwithin displacer 46, displacer 46 may be divided into a plurality ofchambers 142 by a plurality of divider plates 144 as is shown in FIGS. 1and 3.

Pressurization

The durability of displacer 46 and/or the power piston may be furtherimproved by pressurizing the interior of displacer 46 or the powerpiston. The degree to which displacer 46 and/or the power piston ispressurized is preferably based on the degree of pressurization of theworking fluid in the heat engine. Preferably, displacer 46 and the powerpiston has a pressure from about −2 to about 10 atm, more preferablyfrom about 1 to about 10 and, most preferably, from about 2 to about 4atm greater than the pressure of the working fluid in the heat engine.In a similar manner, the structural integrity of walls 12 and 30 may besimilarly enhanced by pressurizing the interior of the heat engine onceit has been constructed. Preferably, the interior of the heat engine(i.e. where the working fluid circulates) is pressurized to a pressurefrom about 1 to about 20, more preferably from about 4 to about 10 atm.Thus, if the pressure of the working fluid is 4 atm, then the displacermay be at a pressure from 2 to 14 atm.

The working fluid may be any working fluid known in the art. Forexample, the working fluid may be selected from air and helium, and, ispreferably helium. Helium has a high thermal conductivity which allowsthe heat engine to be operated at a higher operating frequency thusincreasing the power output per unit volume of interior working space ofthe heat engine (i.e. the volume within which the working fluidcirculates).

Dual Flow Heat Exchanger

In another aspect of this design, the heat engine includes a heatexchanger which uses the heat exchange fins described herein fortransferring heat between the exhaust gas and at least one of the airfor combustion and the working fluid and, preferably, for transferringheat between the exhaust gas and both the air for combustion and theworking fluid. To this end, the heat exchanger comprises a first heatexchanger mounted in a first passageway comprising at least one finhaving first and second opposed sides and constructed to direct theworking fluid as it flows through the first heat exchanger to enhanceheat transfer between the working fluid and the first heat exchanger;and, a second heat exchanger mounted in a second passageway comprisingat least one fin having first and second opposed sides and constructedto direct the working fluid as it flows through the second heatexchanger to enhance heat transfer between the working fluid and thesecond heat exchanger. Optionally, the heat exchanger comprises a thirdheat exchanger mounted in the exhaust gas passageway and comprises atleast one fin having first and second opposed sides and constructed todirect the exhaust gas as it flows there through to enhance heattransfer between the exhaust gas and the third heat exchanger.

Referring to the embodiment of FIG. 3, heater cup 44 is a combustionchamber which surrounded by a heat exchanger 67 comprising inner burnershield 68 having inner surface 74 and outer surface 76, outer burnershield 70 having inner surface 78 and outer surface 80 and air preheatshield 72 having inner surface 82 and outer surface 84 (see, eg., FIGS.1 and 3,). Outer surface 84 of air preheat shield 72 is preferably at atemperature which may be comfortably handled by a user. It can be seenthat when a flame is present, bottom 138 of burner cup 44 becomes hotand this heat is transferred to the working fluid. Wall 62 of the burnercup 44 is heated both by direct radiation from the flame and by contactwith the hot exhaust gas 316 which come from the flame.

Inner surface 74 is spaced from outer surface 32 of outer wall 12 todefine a first pass 86 for the exhaust gases. As the exhaust gas travelsthrough first pass 86 (a combustion gas passageway), the working fluidin flow path 64 is heated. Similarly, inner surface 78 of outer burnershield 70 is spaced from outer surface 76 of inner burner shield 68 soas to define a second pass 88 for the exhaust gases (a combustion gaspassageway). Inner surface 82 of air preheat shield 72 is spaced fromouter surface 80 of outer burner shield 70 so as to define a preheat airflow path 102 (a combustion air passageway). The lower portions of outerburner shield 70 and air preheat shield 72 define entry port 104 topreheat air flow path 102. As the exhaust gas travels through secondpass 88, the air for combustion in preheat air flow path 102 is heated.Depending upon the temperature of the exhaust gas and the thermalefficiency which is desired, a fewer number of passes or a greaternumber of passes may be utilized.

Heater cup 44 defines a combustion chamber 92. Inner burner shield 68may be spaced from top 90 of heater cup 44 so as to define a manifold 94through which the exhaust gases travel prior to entering first pass 86.At the bottom of first pass 86, an annular member 96 is positioned so asto force the exhaust gases to travel through second pass 88, if a secondpass is desired, prior to entering second manifold 98 where the exhaustgases are redirected through cylindrical exit ports 100. Alternately, asshown in FIG. 1, outer burner shield 70 may have a transverse portion 97to close the bottom of first pass 86.

Inner burner shield 68, outer burner shield 70 and air preheat shield 72may be affixed together by any means known in the art. In the preferredembodiment of FIG. 3, the three shields and annular member 96 areconstructed so as to be press fitted together. To this end, innersurfaces 74, 78 and 82 are each provided with a plurality of discreteprotrusions which are spaced apart around each of the inner surfaces.The protrusions abut against the outer surface which is positionedimmediately inwardly thereof so as to provide a seating means forpositioning each shield with respect to the next inner member. Forexample, inner surface 74 of inner burner shield 68 is provided with aplurality of protrusions 106 which engage, at discrete locations, outersurface 32 of outer wall 12. The protrusions thereby allow inner burnershield 68 to be press fitted onto outer wall 12 and to remain seated ata spaced distance from outer surface 32 to define the fluid flow path.Similarly, annular member 96 may be installed by press fitting ontoouter wall 12 prior to shields 68, 70 and 72 being installed. In thepreferred embodiment of FIG. 1, a plurality of positioning memberscomprising one or more of spacer rings 164, 476, louvred fins 428, 440,468 and helical louvred fin 448 are provided to dimensionally stabilizeshields 68, 70 and 72 are provided in first and second passes 86 and 88and preheat air flow path 102. These positioning members may also beconstructed to assist in the transfer of heat.

In the preferred embodiment, a fuel, preferably an organic fuel, iscombusted in heater cup 44 so as to provide heat for the heat engine. Asshown in FIG. 3, the fuel may be a gaseous fuel (eg. butane). However,it will be appreciated that liquid or solid fuel (eg. paraffin) may beused. However, the heat engine may use any heat source (eg. anon-combustion exothermic chemical reaction that is preferablyreversible) and in such a case, heat exchanger 67 may not be required.

In an alternate embodiment, the heat engine may be run in reverse withchamber 160 which is positioned adjacent piston 50 operating at a highertemperature than chamber 140. In such a case, heater cup 44 is replacedwith a heat sink and a heat exchanger 67 may be provided to withdrawheat from chamber 140. Such a heat exchanger would not require a preheatair flow path but is otherwise preferably of a similar design.

Fuel Reservoir

As shown in FIG. 7, a fuel reservoir 108 is provided. Fuel reservoir maybe of any size which is sufficient to render flashlight 10 portable. Forexample, fuel reservoir 108 may comprise a storage tank having a volumefrom about 25 ml to 1 litre or more. One litre of fuel weighs about theequivalent of about 6 D cell batteries. Commercially availableflashlights typically use up to 8 such batteries. The total weight of aportable long life flashlight may be from about 300 g (for a unit withabout 25-50 ml of fuel and a life of about 100 hours) to about 2 kg (fora unit with about 1 litre of fuel and a life of about 2000 hours).Conduit 110 extends from reservoir 108 to annular burner 112. Conduit110 extends through shield 68, 78 and 72 and has openings 114 throughwhich fresh air for combustion may be drawn, via preheat air flow path102, for mixing with the fuel prior to combustion in burner 112. A valve116 is provided in conduit 110 so as to selectively connect reservoir108 and burner 112 in fluid flow communication when it is desired topower flashlight 10. In an alternate embodiment, the heat engine may beconnected to an external fuel source via conduit 110 and the fuel flowcontrol valve may be provided as part of the external fuel source (eg. aregulator on a fuel tank).

Burner

Burner 112 may be of any type known in the art. The burner together withthe burner cup define the heat source. Preferably, the burner is adaptedto provide a varying level of heat to the heat engine (eg. by having afuel valve that is operable between a number of positions) so as to be avariable heat source. It will be appreciated that the heat source may bea chemical reaction (eg. from a fuel cell and the amount of heatprovided may be obtained by altering the rate of reaction) or solar.

Preferably, burner 112 has a top 118 a bottom 120 and a circumferentialsidewall having a plurality of recesses 124 provided therein throughwhich the mixture of air and fuel may pass and be combusted (see FIGS. 3and 7). Each recess 124 is defined by a pair of opposed radial walls 126and an inner circumferential wall 128. The air fuel mixture may beignited by a piezo electric member positioned in housing 220 in whichbutton 18 is mounted and an electric spark may be transmitted to aposition adjacent burner 112 by means of wire 222 and spark plug 224.Buttons to open fuel valves, and to hold them open, are known in the artand any such device may be incorporated into this design.

In operation, when button 18 is depressed into housing 220, drive rod228 (which is affixed to button 18 by eg. screw 229) causes connectingrod 226 (which is pivotally mounted to drive rod 228 by pivot 230) tomove laterally transmitting this lateral force to valve 116 via driverod 232 (which is pivotally connected to connecting rod 226 by pivot 234and to valve 116 by pivot 238) causing valve 116 to pivot about pivot236 to the open position. This allows pressurized fuel to pass throughconduit 110 drawing air for combustion through openings 114 into conduit110. The mixed fuel and air passes through burner 112 where it isignited by any means known in the art such as spark plug 224. Thecombustion of the fuel produces heated exhaust gases which pass throughheater cup 44. In the embodiment of FIG. 3, the exhaust gases exitflashlight 10 by means of first manifold 94, first pass 86, second pass88, second manifold 98 and exit port 100. Button 18 may be locked inthis “on position” by a locking means in housing 220. Alternately, thefuel valve may be controlled by a thermomechanical member, anelectrothermomechanical member or electric control.

Displacer Control

According to another aspect of the instant invention, the upstroke anddownstroke of the displacer are different. Preferably, the heat engineincludes means for operating displacer 46 and piston 50 to provide theworking fluid with greater residence time in cooling chamber 140 than inheating chamber 160. This may be accomplished by controlling displacer46 so that upstroke and the downstroke portions of the displacer cyclevary, eg., by varying the rate of movement of displacer 46 during theupstroke as compared to the downstroke or by pausing displacer 46 duringits cycle to provide the additional residence time in cooling chamber140. Such movement of displacer 46 provides improved thermodynamicallyefficient heat transfer to and from the working fluid. By allowing anadditional 40%, preferably 30% and more preferably 20% of time for theair in the cold region, improved thermodynamic efficiency can beachieved. Exemplary means for operating the displacer include the use ofa solenoid or a magnetic drive system. This may be achieved byattenuating the pulse width and phase delay of the signal sent to thedriver by means of a phase delay circuit 326 (see, eg. FIG. 10).

For example, referring to FIGS. 24a and b, the displacement of displacer46 and piston 50 from the central positions of their cycle is plottedagainst time. In FIG. 24a, the phase angle between displacer 46 andpiston 50 is 180° and the rate of expansion and the rate of compressionby each of displacer 46 and piston 50 are the same. Traditionally inheat engines, the movement of the displacer 46 and piston 50 arephysically linked together by a mechanical coupling and can not bevaried. According to one aspect of the instant invention, the phaseangle between displacer 46 and piston 50 may be varied. In addition, therate of expansion and the rate of compression of one, and preferablyboth, of displacer 46 and piston 50 may be varied. The compression andexpansion of the working fluid, and the phase angle between displacer 46and piston 50, may be varied to optimize the cooling capacity of a heatengine under different thermal loads and different thermal conditions.By way of example, in FIG. 24b, the phase angle between displacer 46 andpiston 50 is 180° but the rate of expansion and the rate of compressionby piston 50 are different. In this example, rapid compression isfollowed by a slower rate of compression then by a rapid rate ofexpansion followed by a slower rate of expansion. The expansion andcompression rates are independent and are each individually adjusted tomaximize heat transfer between the working fluid and the heat engine.The actual cycle profile will vary for different configurations of theheat engine. An advantage of the instant invention is that theelectronic control of piston 50 permits the cycle profile to be easilyadjusted to meet different configurations of the heat engine as well asdifferent uses of the heat engine (eg. electricity production,refrigeration, cryocooling). In this way, the compression and expansionof the working fluid may be controlled to be conducted atthermodynamically optimum rates and the heat engine may be used not onlyto generate work using a heat source but to generate cooling using workinput to a linear generator operating as a piston.

For example, in the case of refrigeration or cryocooling, at least onedrive member may be drivingly connected to the displacer and the pistonto produce a displacer cycle profile and a piston cycle profile whichcauses the working fluid to undergo differing rates of expansion andcompression in the first chamber than in the second chamber whereby themovement of the working fluid transfers heat from the heat sink (eg. theinside of a chamber to be cooled or conduits for providing cooling toanother location) to the working fluid in the first chamber and thenfrom the second chamber to the heat dissipation members. The at leastone drive member may be a motor drivingly connected to the piston and asecond drive member (eg. coils 328) to move the displacer. Preferably,the at least one drive member is operated to cause the working fluid toundergo a slower rate of expansion in the first chamber then the rate ofcompression of the working fluid in the first chamber and to undergo aslower rate of compression in the second chamber then the rate ofexpansion of the working fluid in the second chamber.

Referring to FIGS. 2a -2 d, the heat engine has a first portion 240 inwhich displacer 46 is movably mounted and a second portion 242 in whichpower piston 50 is movably mounted. The portion within which displacer46 is movable is the hot end of the heat engine and the portion withinwhich the power piston is movable is the cool end of the heat engine.Driver 48 has an internal circumferential wall 130 defining an opening132 into which displacer rod 134 is received. Displacer 46 is mountedfor movement within inner wall 30 between the alpha position shown inFIG. 2b wherein displacer 46 is withdrawn from heater cup 44 and theomega position as shown in FIG. 2a in which displacer 46 is distal todriver 48 and advanced towards heater cup 44. As shown in FIGS. 2a and 2c, when displacer 46 is positioned in the omega position, there is achamber 244 between displacer 46 and driver 48. In this position,displacer rod 134 is substantially removed from opening 132. As shown inFIGS. 2b and 2 d, when displacer 46 is in the alpha position,effectively all of displacer rod 134 is received in opening 132 leavingheating chamber 140 (defined by top 136 of displacer 46, bottom 138 ofheater cup 44 and inner surface 38 of inner wall 30) between displacer46 and heater cup 44.

Heating chamber 140 is heated by the combustion occurring in heater cup44. As displacer 46 moves upwardly to the position shown in FIG. 2a, theheated working fluid in heating chamber 140 is forced upwardly throughfluid flow path 64 where it is heated by the heated heater cup 44, andthrough opening 66 into fluid flow path 40 (a portion of the workingfluid passageway) where it is heated by the exhaust gasses, thusincreasing the pressure of the working gas. When displacer 46 is in thedistal position shown in FIGS. 2a and 2 c, effectively all of theworking fluid has been forced out of heating chamber 140. To this end,it is preferred that bottom 138 of heater cup 44 and top 136 ofdisplacer 46 are constructed so as to intimately fit adjacent each otherso as to force as much of the working fluid out of the heating chamber140 as possible. Preferably, as shown in FIG. 2a, bottom 138 is curvedso as to transfer heat to the working fluid. Alternately, as shown inFIG. 3, bottom 138 may be flat and, accordingly, top 136 of displacer 46may also be flat.

Inner circumferential wall 130 of driver 48 provides a guide fordisplacer rod 134 so as to maintain the longitudinal alignment ofdisplacer 46 along axis A as displacer 46 moves between the alpha andomega positions. Displacer rod 134 and inner circumferential wall 130may be dimensioned and constructed so as to allow relativelyfrictionless movement of displacer rod 134 into and out of opening 132.In order to further assist in the reduction of frictional forces, bottom146 of displacer 46 may have a recessed circumferential wall 148. Ateflon bushing 150 or the like may be mounted around recessedcircumferential wall 148 for engagement with inner surface 38 of innerwall 30 as displacer 46 moves. Further, a second teflon bushing or thelike 152 may be provided on inner circumferential wall 130.

Driver 48 may be any means known in the art which is drivingly connectedto displacer 46 to cause displacer 46 to move in a cycle that iscomplementary to the cycle of power piston 50 so as to optimize thethermal efficiency of the heat engine. This may be achieved by movingdisplacer 46 in response to an external stimulus such as an electricalimpulse caused by the movement of power piston 50. Preferably, driver 48is a solenoid or an electromagnet and, more preferably, anelectromagnet. If driver 48 is a solenoid, current may be provided tothe solenoid by means of wire 154 (see FIG. 2e). Accordingly, whencurrent is supplied to the solenoid, displacer 46 will move due thecurrent (i.e. the external force) supplied thereto. If driver 48 is anelectromagnet, then, displacer 46 and/or displacer rod 134 includes apermanent magnet for moving displacer 46 due to a magnetic fieldproduced by the electromagnet. Accordingly, when current is supplied tothe coils of the electromagnet, the coils may be charged in a reversepolarity to the portion of displacer rod 134 in opening 132 thus forcingdisplacer rod 134 outwardly from opening 132 thus driving the workingfluid from heating chamber 140. When the current is reversed in thecoils, displacer rod 134 is attracted to driver 48 and accordinglydisplacer rod 134 is pulled downwardly into opening 132 (thus drawingthe working fluid into heating chamber 140).

In a preferred embodiment, displacer 46 is biased, preferably to thealpha position shown in FIG. 2b. This may be achieved, for example, bymeans of spring 156 as shown in FIGS. 2c and 3. In such a case, driver48 may act only to move displacer 46 to the omega position (i.e. towardsheater cup 44) thus pushing heated working fluid to cooling chamber 160.When the working fluid is cooled to a sufficient degree, the current todriver 48 may be switched off allowing the biasing means (eg. spring156) to move the displacer to the alpha position thus drawing theworking fluid into heating chamber 140. When the working fluid isheated, the current to driver 48 may be switched on thus movingdisplacer 46 against spring 156 to the omega position. In oneembodiment, driver 48 may be powered at all times once the heat engineis running.

It will be appreciated that driver 48 need not completely extend toinner wall 38 of inner wall 30. For example, driver 48 may have asmaller diameter than inner wall 30 and be mounted thereto by, eg.,brackets. If the outer wall of driver 48 contacts inner wall 38 as shownin FIGS. 2a -2 e, then chamber 244 is preferably in fluid flowcommunication with cooling chamber 160, such as by passage 260, toprevent a reduced pressure region from forming in chamber 244. Thus,when displaced moves to the extended position shown in FIG. 2a, cooledworking fluid in cooling chamber 160 may travel through passage 260 intochamber 244 to maintain an equilibrium pressure between chambers 244 and160. Further, when displacer 46 moves to the retracted position as shownin FIG. 2b, cooled fluid is pushed from chamber 244 by displacer 46 intocooling chamber 160 via passage 260 and then to heating chamber 140.

Inner wall 30 is provided with a passageway, eg. a plurality of openings158 adjacent the top of cooling zone 26. Openings 158 define an entryport for the working fluid to enter second portion 242 of the heatengine after passing through air flow path 40. As shown in FIG. 5, thelower portion of driver 48 may have a chamfered surface 168. Thechamfered surface assists in directing the working fluid into and out ofcooling chamber 160. Power piston 50 is not physically connected todisplacer 46 but is moved due to the change of pressure in coolingchamber 160. Accordingly, when displacer rod 134 moves displacer 46 tothe withdrawn position shown in FIGS. 2a and 2 c, working fluid isforced through flow path 40, through opening 158 into cooling chamber160. The action of the working fluid on top 162 of piston 50 forcespiston 50 downwardly into open area 246. As the working fluid cools incooling chamber 160, the pressure of the working fluid decreases thusdrawing piston 50 upwardly and reducing the volume of the working zoneof the heat engine (i.e. chambers 140, 160, 244 and fluid flow paths 64and 40). When displacer 46 moves away from heater cup 44 to the positionshown in FIGS. 2b and 2 d, eg. in response to driver 48 or the spring,the working fluid is drawn from cooling chamber 160 through openings 158through flow path 40 through openings 66, through flow path 64 intoheating chamber 140.

In the alternate embodiment of FIGS. 9-11, 19 and 20, driver 48comprises a magnetic field that is imposed on displacer 46. Asexemplified in these Figures, displacer 46 has a magnet 286 affixed toit, preferably on bottom 146. Displacer magnet 286 and displacer 46affixed thereto are held concentrically in place and their range ofmotion limited by two magnets 284 and 288 which are preferably circularand which repel the displacer magnet 286. Thus displacer 46 sits on amagnetic bearing caused by the mutual repulsion of magnet 288 todisplacer magnet 286 and the mutual repulsion of magnet 284 to displacermagnet 286. The repulsive magnetic field between magnets 286 and 288serves to store kinetic energy from the upstroke of displacer 46 andlimits the travel of displacer 46. The stored kinetic energy from theupstroke of displacer 46 is returned to displacer 46 on the downstroke.

Linear generator

In another aspect of the design, the apparatus includes a lineargenerator. Preferably, piston 50 comprises part of the linear generator.The linear generator in electrical generation zone 28 may be of anyconstruction known in the art. The following description is of thepreferred embodiment of the linear generator which is shown in FIGS. 2a,2 b, 2 c, 2 d and 4. In these embodiments, the linear generator ispositioned in a sealed chamber. In the embodiment of FIGS. 2a and 2 b,the upper end of the linear generator is isolated from the working fluidby piston 50 and the lower end is sealed by closure member 195. In theembodiments of FIGS. 2c, 2 d and 4, the upper end of the lineargenerator is isolated from the working fluid by top 162 and the lowerend is sealed by closure member 195. As shown in FIGS. 2a and 2 b,piston 50 is a sealed member having a top 162, a bottom 170 andsidewalls 172. Drive rod 174 may accordingly be affixed to bottom 170 byany means known in the art. In the embodiment of FIGS. 2c, 2 d and 4,piston 50 comprises top 162 and sidewalls 172. In this embodiment, driverod 174 is affixed to inner surface 176 of top 162, by any means knownin the art, such as by threaded engagement therewith. As shown in FIG.4, inner surface 176 may be provided with a splined shaft 178 which isreceived in a mating recess in drive rod 174.

A plurality of magnets 52 are fixedly attached to drive rod 174 by anymeans known in the art, such as by use of an adhesive or by mechanicalmeans (eg. the interior opening through which drive rod passes in magnet152 may be sized to produce a locking fit with drive rod 174 or driverod 174 may be threaded and magnet 152 may be positioned between spacersthat are threadedly received on drive rod 174). A mating number of coils56 of electrically conductive wire are provided at discrete locationsalong the length of electrical generation zone 28. Coils 56 are affixedto inner wall 34 of outer wall 12 by any means known in the art, such asby means of an adhesive or by mechanical means (eg. coils 56 may beprovided in a housing which is affixed to inner wall 34 by welding or bybrackets). Thus coils 56 are stationary as drive rod with magnets 52affixed thereto is moved by power piston 50. It will be appreciated thatcoils 56 may be affixed in a stationary manner by any other means knownin the art. In an alternate embodiment, coils 56 may be affixed to driverod 174 and magnets 52 may be stationary.

An annular ferrite bead 54 is positioned centrally within each set ofcoils 56. Each ferrite bead 54 has a central opening through which driverod 174 passes. One of the coils 56 has wires 180 extending outwardlythere from. The remainder of the coils 56 have wires 182 extendingoutwardly there from (see FIG. 7). It will be appreciated by thoseskilled in the art that only one ferrite bead 54 and one coil 156 may beprovided. It will further be appreciated that the output wires from anyof the coils 56 may be grouped together in parallel or series as may bedesired.

As power piston 50 moves into area 246 away from driver 48 in responseto working fluid impinging upon top 162, magnets 52 move longitudinallyalong axis A so as to cause current to flow in coils 56 (see FIG. 2b).When piston 50 moves upwardly due to the cooling of the working fluid incooling chamber 160, magnets 52 are then driven in the reverse directioncausing current to again flow in coils 56.

In the preferred embodiment, each magnet 152 moves between a pair offerrites 154. In particular, referring to FIG. 4, magnet 52 a is movablymounted in the linear generator between ferrite 54 a and ferrite 54 b.As drive rod 174 moves with piston 50, magnet 52 a moves from a positionadjacent ferrite 54 a as shown in FIG. 4 to a position adjacent ferrite54 b. Similarly, magnet 52 b moves from a position adjacent ferrite 54 bto a position adjacent ferrite 54 c. In this way, it will be seen thatat the end of each stroke of piston 50, ferrite 54 b is acted upon atany one time by only one magnet 152. Similarly, magnet 52 a will firstact upon ferrite 54 a and then upon ferrite 54 b. In this way, ferrite54 b is sequentially exposed to, eg., a north field from magnet 52 a andthen a south field from magnet 52 b.

One advantage of the instant design is that there is a higher rate ofchange of flux per unit time due to ferrites 154 first being acted uponby one field and then the opposed field. Further, since ferrite 154 isacted upon by opposed poles of different magnets, the magnetic fieldinduced on ferrite on 54 b by magnet 52 a will completely collapse asmagnet 52 a moves to the position shown in FIG. 4 and ferrite 54 b isacted upon by magnet 52 b.

An alternate construction of a linear generator is shown in FIGS. 9-11,19 and 20. In these embodiments, the magnets are positioned within innerwall 30 and the coils are positioned exterior thereto (eg. on outersurface 36 of inner wall 30 or on outer surface 32 of outer wall 12).Power piston 50 consists of a plurality of spaced apart magnets, eg.four magnets 270, 272, 274 and 276 and three non-magnetic spacers 278,280 and 282. The non-magnetic spacers may be made of plastic whichsurrounds and encases the magnets. It will be appreciated that theassembly of magnets and spacers may be connected to the power piston ofFIGS. 2a or 2 c by a drive rod 174. Preferably, the assembly comprisespiston 50.

Power piston 50 of FIGS. 9-11, 19 and 20 is held concentrically in placeand its range of motion limited by two magnets 284 and 190 which arepreferably circular permanent magnets and which repel magnets 270 and276 respectively. Thus the power piston 50 sits on a magnetic bearingcaused by the mutual repulsion of magnets 284 and 270, and magnets 190and 276. The repulsive magnetic field between magnets 276 and 190 servesto store kinetic energy from the downstroke of the power piston 50 andwill return this energy to the power piston 50 on the upstroke of powerpiston 50. Thus the magnets 276 and 190 act as a magnetic spring at thebottom of the stroke, and, similarly, magnets 284 and 270 form arepulsive magnetic field at the top of the power piston stroke whichalso acts as a magnetic spring.

Heat Engine Cycle

The following is a description of the operation of the heat engine basedon the embodiment of FIGS. 9-11 wherein fin means are provided invarious fluid flow passageways to assist in heat transfer. Heatingchamber 140, cooling chamber 160 and passageways 64, 312 and 40 are asealed region within which the working fluid circulates. This heatengine cycle begins with displacer 46 positioned towards the cold end ofthe engine, that is, in the alpha position. This causes most of theworking fluid to be forced into heating chamber 140. Wall 62 of burnercup 44 heats the inner heat exchanger 310 which in turn heats theworking fluid in passage 64. The hot exhaust gas 316 then pass throughmanifold 94 and then pass through the exhaust outer heat exchanger 314(to which the hot exhaust gas imparts most of its heat energy) and exitas cooled exhaust gas 332. The heat energy from the exhaust outer heatexchanger 314 is then transferred through the heat engine outer wall 12and into the exhaust inner heat exchanger 312 which in turn imparts thisheat into the working fluid.

The heating of the working fluid causes the working fluid to expand. Theexpansion takes place through heat exchangers 310 and 312, through theregenerator 42, through openings 158 and into cooling chamber 160 wherepressure begins to build against power piston 50. This causes powerpiston 50 to move downwards towards magnet 190 and causes the magnets270, 272, 274 and 276 to induce voltages and current in the generatorcoils 318, 320, 322 and 324 respectively. The coils provide power to anoutput. A portion of the power is preferably used to operate thedisplacer (eg. coils 318) and the remaining is preferably provided to anoutput for providing electrical power to an load.

The electrical energy from one or more of the coils, eg. generator coil318, provides power via wires 180 to the phase delay circuit 326 whichmodifies the power signal from the generator coil 318 and then feeds itthrough wires 154 to the displacer control coil 328 which acts as anadjustable drive member. Circuit 326 is a signal modulator which maycomprise, eg., either of a variable capacitor and a fixed inductor or ofa variable inductor and a fixed capacitor. Phase delay circuit 326 maybe any circuit that will drive displacer 46 to move in a cycle that isout of phase to the cycle of power piston 50. Circuit 326 modifies thepower signal from the generator coil 318 and then feeds it through wire154 to displacer control coil 328. This signal sent to the displacercontrol coil 328 causes an upward force on the magnet 286 which in turncauses magnet 286 and displacer 46 affixed thereto to move upwardstowards magnet 288.

The upstroke of displacer 46 causes the working fluid to flow throughthe heat exchangers 312 and 310, through the regenerator 42, through theopenings 158 and into the cold end of the engine 160. As the workingfluid passes through the regenerator 42, most of the heat of the workingfluid is transferred to the regenerator 42. The remaining heat from theworking fluid now located in the cold end 160 of the engine isdissipated by heat exchanger 330. Heat from the working fluid nowlocated in cooling chamber 160 is dissipated by heat exchanger 330 whichpreferably comprises a plurality of cooling fins 331 which may belouvred fins 428, 440, 468 or helical louvred fin 448. This causes theworking fluid to contract and reduces the pressure within the engine.This causes power piston 50 to move upwards under the influence of themagnetic energy stored between magnets 276 and 190.

The upward motion of power piston 50 causes magnet 270 to induce areverse current pulse in the generator coil 318. This reverse currentpulse from generator coil 318 provides power to the phase delay circuit326 which modifies the power signal from the generator coil 318 and thenfeeds it through wires 154 to the displacer control coil 328. Thissignal sent to the displacer control coil 328 causes a downward force ondisplacer magnet 286 which in turn causes displacer magnet 286 anddisplacer 46 affixed thereto to move downwards towards magnet 284. Therepulsive magnetic field between displacer magnet 286 and magnet 288serves to impart the stored kinetic energy from the upstroke of thedisplacer 46 to the downstroke. The repulsive magnetic field betweendisplacer magnet 286 and magnet 284 serves to store kinetic energy fromthe downstroke of displacer 46 for the next upstroke. The repulsion ofdisplacer magnet 286 and magnet 284 also serves to limit the travel ofdisplacer 46.

In an alternate embodiment, phase delay circuit 326 may be replaced by acontroller that senses when the voltage from the generator coil 318 isapproaching zero which is the bottom of the stroke of the power piston50. At this point, the controller may cut the signal to the displacercontrol coil 328 and begin a reverse (negative) pulse which causes thedisplacer 46 to move downwards towards magnet 270. Alternately, thecontroller may cut the signal and allow displacer 46 to move downwardlyunder the influence of a biasing member, eg. a spring or the magneticfields to which it is exposed.

If displacer is to be directly driven by piston 50 (eg. without anyphase angle modification) electrical energy from generator coil 318 mayprovide power via wires 180 to displacer control coil 328.

The downward movement of the displacer 46 causes the working fluid to beforced from the cold end of the engine 160 through openings 158, throughregenerator 42 through the heat exchangers 312 and 310, and into the hotend of the engine near bottom 138 of burner cup 44. As the working fluidpasses through regenerator 42, most of the heat stored in regenerator 42is transferred into the working fluid. The cycle then repeats itself.

In accordance with one aspect of this invention, the cycle profile ofthe displacer and/or the piston may be adjusted. The cycle profiledescribes the velocity of the displacer/piston as it moves between thefirst and second positions and the dwell time of the displacer/pistonwhen it is in each of the first and second positions. The cycle profilealso includes the phase angle between the piston and the displacer. Theapparatus preferably includes a feedback member responsive to powerdemand from the power output member by a load to modulate the amount ofheat provided by the heat source to the working fluid. A preferredembodiment of the feedback member comprises an adjustable signalgenerator drivenly connected to one of the piston and the displacer(preferably the displacer) to control the movement of the one of thepiston and the displacer. The adjustable signal generator may bemanually controlled but preferably comprises the piston and a signalmodulator whereby the piston generates a signal which is sent to thesignal modulator and the signal modulator modulates the signal that isthen sent to an adjustable drive member. Examples of such configurationsare shown in FIGS. 10, 19 and 20.

Thus the piston and, eg., the phase delay circuit 326, variable inductor370 or primary controller 372 comprise an adjustable signal generatorwhich is drivenly connected to an adjustable drive member. Theadjustable drive member may be a coils 328, driver 48 and may alsoinclude any other drive member known in the art of heat engines formoving one of the displacer and the piston (and preferably thedisplacer).

Self starting

Piston 50 is preferably biased to the alpha position shown in FIGS. 2b,2 c and 4 such as by means of a spring 184 (see FIG. 2b) or by amagnetic bushing (eg. 186, 190) as shown in FIGS. 2c and 4. Inparticular, as shown in FIG. 4, a magnet 186 is attached to distal end188 of drive rod 174 from piston 50. Distal end 188 travels through ancentral opening in closure member 195 which may be installed in outerwall 12 by a press fit. A second magnet 190 is affixed to inner surface192 of closure member 194. To prevent the magnets touching each other,an elastomeric member 196 may be affixed to the distal end of magnet 190from inner surface 192. End 198 of magnet 186 is of an opposite polarityto end 200 of magnet 190. Accordingly, magnets 190 and 186 will repelpiston 50 to the alpha position shown in FIG. 4. Piston 50 moves betweenthe alpha position and the omega position (shown in FIG. 2d) due to theinfluence of the working fluid on top 162 of piston 50.

By biasing displacer 46 and piston 50 to the alpha positions, the heatengine may be self starting. In particular, when heat is applied toheating chamber 92 (eg. combustion is initiated in heater cup 44), theworking fluid in heating chamber 140 will commence expanding. Theexpansion of the working fluid will cause some of the working fluid topass out of heating chamber 140 into cooling chamber 160. The entranceof the working fluid into cooling chamber 160 will cause piston 50 tomove downwardly. Provided piston 50 moves downwardly by a sufficientamount and/or at a sufficient rate, an electrical current will begenerated which may be transmitted by wires 180 to driver 48. The signalwill cause driver 48 to move displacer 46 towards the omega positionthus initiating a first stroke of displacer 46 and evacuating additionalheated working fluid from heating chamber 140 into cooling chamber 160thus further driving piston 50 downwardly to generate further amounts ofcurrent.

The working fluid is isolated in the heat engine. To this end, theopposed ends of inner wall 30 are sealed and fluid flow path 40 is alsosealed. Heater cup 44 is preferably used to seal the end of inner wall30 adjacent heating chamber 140. Piston 50 is preferably used to sealthe end of inner wall 30 adjacent cooling chamber 160 such as bycreating a seal with inner surface 38 of inner wall 30 thus isolatingthe linear generator from the working fluid.

It will be appreciated that the linear generator need not be sealed. Forexample, air may be able to pass through the central opening in closuremember 195 as well as past coils 56 so as to prevent significantpressure build up in the linear generator as magnets 52 move.

Closure members 194 and 195 assist in the construction of flashlight 10as well as to protect coils 56 from the incursion of foreign materialwhich would damage the linear generator. Closure members 194 and 195 maybe affixed to the bottom of the one of the cylinders by any means knownin the art. For example, referring to FIG. 2a, closure member 195 isintegrally formed as part of outer wall 30 whereas, for example, closuremember 194 is welded to the distal end of outer wall 12 from heater cup44. In the embodiment shown in FIG. 4, closure member 194 has an annularflange 202 which is threadedly received on outer surface 32 of outerwall 12. However, if the inner container, or the outer container, areprepared by high speed die stamping, then closure members may beintegrally formed as part of the inner/outer container.

Referring to FIG. 8, wires 180 from the first set of coils 56 areelectrically connected to wires 154 of driver 48. Wires 180 pass throughcontroller 206 (which is preferably phase delay circuit 326). Wires 180and 154 as well as controller 206 (which may be a phase delay circuit)may be positioned between inner and outer walls 30 and 12 (i.e. in gaps166 and fluid flow path 40).

Thermomechanical Control

A cross sectional view of a preferred embodiment of a heat exchangerutilizing thermomechanical control is shown in FIGS. 9-11.

To start the engine, the start switch 18 is engaged. The start switch 18is operatively linked to the fuel switch lever 290 by means of linkingmember 291 which is preferably mechanical. Fuel switch lever 290 isactivated such that the fuel flow control valve 292 and the variableflow fuel control valve 294 are both momentarily opened. Preferably fuelswitch lever 290 is a mechanical switch drivenly moveable by linkingmember 291 between two positions and which is mechanically linked tofuel flow control valve 292 and the variable flow fuel control valve294. When the lever switch 290 is released, the variable flow fuelcontrol valve 294 closes and the fuel flow control valve 292 remainsopen. This ensures starting fuel reserve 296 is full and fuel from thestarting fuel reserve 296 begins to flow. The fuel in the starting fuelreserve is sufficient for a short period of operation (eg. 1-2 minutes).In the event that the burner 298 fails to ignite, then the amount offuel which may accidentally escape into the environment is limited tothe small harmless amount in the starting fuel reserve 296. Hence thestarting fuel reserve 296 and its associated mechanisms acts as a safetydevice to prevent the spillage or release of large quantities of fuel.

When start switch 18 is depressed, piezo crystal high voltage powersupply 300 produces high voltage which flows along conductor 302 to theelectrode 304 where a spark is created which ignites the fuel in theburner 298 and causes a flame to form. Optionally, the fuel switch lever290 and the start switch 18 need not be linked together but may besequentially operated by the user.

The flame immediately begins to heat burner cup 44 as well as heatingfuel flow control member 308 which, on heating, begins to open thevariable flow fuel control valve 294. Flow control valve member 308 maybe any member that will reconfigure itself on heating so as to adjustthe position of variable flow fuel control valve 294. Examples of suchmembers include members that deform on heating (eg. a bimetal strip),significantly contract or elongate with temperature changes (eg. musclewire) or significantly alter their spring constant with temperaturechanges thereby exerting variable force based on temperature (eg.homeostat type devices).

Fuel flow control member 308 is configured such that as the temperaturein combustion chamber 92 reaches the optimum operating temperature, thevariable flow fuel control valve 294 will be fully open so that the heatengine will provide full power. If full power is not required, theburner cup will begin to overheat because the available thermodynamicenergy is not being converted to mechanical or electrical energy. Theoverheating will cause the variable flow fuel control valve 294 to beginto close over its central maximum flow point thereby reducing the fuelflow and thereby reducing the temperature to the optimal range.

Thus a self regulating system is established wherein the amount of fueldelivered by the variable flow fuel control valve 294 is controlled bythe temperature of combustion chamber 92 which always remains within itsoptimum operating range as controlled by the bimetal fuel flow controlmember 308. Accordingly, for example, feedback member is drivinglyconnected to the variable fuel flow valve 294 and comprises a thermalsensor (flow control valve member 308) thermally connected to combustionchamber 92 whereby the temperature of combustion chamber 92 variesinversely to the power drawn from the linear generator by the load, thethermal sensor senses the temperature of combustion chamber 92 and thefeedback member adjusts the flow rate of fuel supplied to the combustionchamber to maintain the temperature of the combustion chamber within apreset range.

Thermoelectromechanical Control

A cross sectional view of the preferred embodiment of this invention isshown in FIG. 19.

To start the engine, the start switch 18 is preferably engaged as withthe embodiment of FIGS. 9-11 to commence ignition and the heating ofheater cup 44. When the power piston 50 begins to move and the generatorcoils 318, 320, 322 and 324 begin to generate power, electricity flowsthrough wires 334, 336 and 338 which are electrically connected to lowresistance resistor 342 via wire 340. Electricity flows from lowresistance resistor 342 to internal load resistor 344 via wire 346 andto external load 348 via wire 350.

Electricity from the generator coils 320, 322 and 324 also flows throughwires 352, 354 and 356, through wire 358, through the low resistanceresistor 360, through wires 362 and 364 to the internal load resistor344 and to the external load 348. The internal load resistor 344 ensuresthat a small amount of current is always being withdrawn from thegenerator. This ensures that a small amount of current is always flowingthrough the low resistance resistor 360 which supplies heat to fuel flowcontrol member 308 which opens the variable flow fuel control valve 294by means of lever 366. The current drawn by the internal load resistorcauses the low resistance resistor 360 to heat slightly which causes thefuel flow control member 308 to be reconfigured (eg. to bend or contractor deform) thereby opening the variable flow fuel control valve 294enough to maintain the fuel flow required for standby operation.

When the current drawn by the external load 348 increases, the amount ofheat created by the low resistance resistor 360 increases which causesthe fuel flow control member 308 to be further configured (eg. to bendfurther) thereby opening the variable flow fuel control valve 294further so as to provide enough fuel to provide the thermal energyrequired to generate the power drawn by the load. Thus a fuel controlsystem which proportions the fuel flow to the load has been developed.

Upon ignition, the flame immediately begins to heat the burner cup 44.As the temperature of burner cup 44 becomes sufficient to cause thecyclic operation of the heat engine, the electrical current produced bygenerator coils 318, 320, 322 and 324 begins to flow. As the currentbegins to flow through low resistance resistor 360, through internalload resistor 344 via wire 346, low resistance resistor 360 begins toheat and supplies heat to fuel flow control member 308 which begins toopen the variable flow fuel control valve 294 by means of lever 366. Asthe temperature of low resistance resistor 360 reaches its optimumoperating temperature, the variable flow fuel control valve 294 will beopen fully for full power. If full power is not required, the lowresistance resistor 360 will become cooler thereby causing the variableflow fuel control valve 294 to begin to close thereby reducing the fuelflow. Conversely, if the load 348 draws more power, variable fuel flowcontrol valve 294 will again be opened due to the increased heat of lowresistance resistor 360 being supplied to the fuel flow control member308 which in turn opens variable fuel flow control valve 294. Thus aself regulating system is established wherein the amount of fueldelivered by the variable flow fuel control valve 294 is controlled bythe temperature of low resistance resistor 360 whose temperature isproportional to the power required by load 348. Alternately, if thesystem does not include internal load resistor 344, and if the externalload 348 requires no power, then the mechanism associated with lowresistance resistor 360 will cause variable fuel flow control valve 294to shut off the fuel supply and cause the engine to stop once fuelreservoir 296 is exhausted.

The internal load resistor 344 ensures that a small amount of current isalways being withdrawn from the generator. This ensures that a smallamount of current is always flowing through the low resistance resistor360 which supplies heat to the heat reconfigurable member 368 whichoperates the variable inductor 370. Heat reconfigurable member 368 maybe any member that will reconfigure itself on heating (eg. a bimetalstrip, muscle wire or homeostat type devices). The current drawn byinternal load resistor 344 causes the low resistance resistor 360 toheat slightly which causes the heat reconfigurable member 368 to bendthereby operating the variable inductor 370 (a signal modulator) so asto maintain an optimal phase angle between the displacer 46 and thepower piston 50. When the current drawn by the external load 348increases, the amount of heat created by the low resistance resistor 360increases which causes the heat reconfigurable member 368 to deformfurther thereby further changing the setting of the variable inductor370 thereby again changing the phase angle relationship between thedisplacer 46 and the power piston 50. It has been found that a givenengine with a given displacer and power piston phase angle relationshiphas an energy efficiency curve which varies for different power levelsor different burner/ambient temperatures. Similarly, it has been foundthat by varying the phase angle, relationship between the displacer andthe power piston, an efficient operating point can be established forany power and/or burner/ambient temperatures. Thus a simpledisplacer/power piston phase control system has been developed whichmodifies the phase angle under varying load conditions to maintain theefficiency of the system.

In an alternate embodiment, solid state electronics may be used tocontrol a transistor which drives resistor 360 and fuel flow controlmember 308 of the variable fuel flow valve 294 and the variable inductor370.

Accordingly, for example, a feedback member is drivingly connected tothe variable fuel flow valve 294 and comprises a circuit includingresistor 360 electrically connected to the circuit to draw currentproportional to the power demand drawn from the output (external load348), and a thermal sensor (fuel flow control member 308) thermallyconnected to resistor 360 whereby the thermal sensor indirectly sensesthe power demand of a load applied to the output and the feedback memberadjusts the flow rate of fuel supplied to combustion chamber 92 tomaintain the temperature of combustion chamber 92 within a preset range.

Electric Modulation Control

A cross sectional view of the preferred embodiment of this invention isshown in FIG. 20.

When the start switch 18 is depressed, a signal is sent from the primarycontroller 372 (a signal modulator) to the fuel flow controller 374 bymeans of wire bundle 376. The signal to the fuel flow controller 374causes the fuel flow controller 374 to energize a valve, eg. springloaded normally closed solenoid fuel valve 382, to open by means of wirepair 384. The opening of the spring loaded normally closed solenoid fuelvalve 382 allows fuel to flow from the small staring fuel reservoir 296along passage 110 and along to the burner 298.

The primary controller 372 also supplies power to the high voltage powersupply 378 by means of the wire pair 380 which causes high voltage to begenerated which then passes along wire 302 to the high voltage electrode304 where sparks are created which causes the vaporized fuel in theburner 298 to be ignited. The resulting flame immediately begins to heatthe bottom of the burner cup 44.

The hot exhaust gasses and radiation from the flame heats thetemperature sensing means 386 (eg. a thermocouple) which is connected tothe fuel flow controller 374 by means of the wire pair 388. In responseto the fuel flow controller 374 interpreting a high temperature present,the fuel flow controller 374 energizes another valve, eg. spring loadednormally closed solenoid fuel valve 390, by means of wire pair 392. Thefuel flow controller 374 also sends a signal to the primary controller372 by means of wire bundle 376 which in turn causes the primarycontroller 372 to de-energize the high voltage power supply and stop thesparking at electrode 304. The temperature in burner cup 44 isconstantly measured by the temperature measuring means 386 and monitoredby the fuel flow controller 374 by means of the connection through wirepair 388. If at any point the temperature drops below a presettemperature of for example 400° F., the fuel flow controller 374 sends asignal to the primary controller 372 by means of wire bundle 376. If theprimary controller 372 registers the fact that the fuel flow is on andthe temperature has fallen below the preset temperature of for example400° F., the primary controller 372 will re-energize the high voltagepower supply 378 causing high voltage to flow along wire 302 toelectrode 304 where sparks will again be created in order to relight thefuel in the burner 298 and to re-establish the flame. The heat from theflame will again heat the temperature measuring means 386 which ismonitored by the fuel flow controller 374 through wire pair 388.

Once the preset temperature of for example 400° F. is reached, the fuelflow controller 374 will send a signal to the primary controller 372 bymeans of the wire bundle 376 which will in turn cause the primarycontroller 372 to de-energize the high voltage power supply and stop thesparking at electrode 304. If the temperature is not re-establishedwithin a preset amount of time, the fuel flow controller 374 preferablyde-energizes spring loaded normally closed solenoid valves 382 and 390by de-energizing wires 384 and 392 respectively. Thus, a safety meansfor ensuring that the burner is lit is incorporated in the design.

The electrical energy from one or more coils, eg. generator coil 318,provides power to the rechargeable battery 394 by means of the wire pair180. The battery 394 in turn provides power to the primary controller372 to which it is attached. The primary controller 372 senses the inputto the battery from the generator coil 318 which causes the primarycontroller 372 to send a signal to the displacer control coil 328 bymeans of wire 154. This positively polarized signal sent to thedisplacer control coil 328 causes an upward force on the magnet 286which in turn causes the magnet 286 and the displacer 46 affixed theretoto move upwards towards magnet 288.

In addition to the basic cycle, the new heat engine optionallyincorporates means to modulate the fuel burn and optimize energyefficiency. There are a plurality, eg. four, solenoid fuel valves 390,294, 396 and 398 which are connected to the fuel flow controller 374 bymeans of wire pairs 392, 402, 404, and 406 respectively. The primarycontroller 372 senses the current flowing to the load 408 through wirepairs 410, 412, and 414 by means of the hall effect current sensor 416which is connected to the primary controller 372 by means of wire pair418. The power from the generator coils flows out to the load 408 (eg.an outlet or an electric apparatus) by means of wires 420 and 422. Whenthe primary controller 372 determines that the current flowing to theload is, eg., between 0 to 25 percent of the maximum output power of theheat engine and generator, it ensures that only solenoid fuel valve 390is energized by sending a signal along two of the eight wires in thewire bundle 376 which connects the primary controller 372 to the fuelflow controller 374. The fuel flow controller 374 in turn energizes onlythe spring loaded normally closed solenoid valves 382 and 390.

When the primary controller 372 determines that the current flowing tothe load is, eg., between 26 to 50 percent of the maximum output powerof the heat engine and generator, it sends a signal to the primary fuelcontroller 374 along two of the wires in the wire bundle 376. Thissignal causes the primary fuel controller 374 to energize an additionalspring loaded normally closed solenoid fuel valve 396 by means of thewire pair 402 which causes the spring loaded normally closed solenoidfuel valve 396 to open thereby increasing the fuel flow to the burner298.

When the primary controller 372 determines that the current flowing tothe load is, eg., between 51 to 75 percent of the maximum output powerof the heat engine and generator, it sends a signal to the primary fuelcontroller 374 along two of the wires in the wire bundle 376. Thissignal causes the primary fuel controller 374 to energize yet anotherspring loaded normally closed solenoid fuel valve 398 by means of thewire pair 404 which causes the spring loaded normally closed solenoidfuel valve 398 to open thereby further increasing the fuel flow to theburner 298.

When the primary controller 372 determines that the current flowing tothe load is, eg., greater than 75 percent of the maximum output power ofthe heat engine and generator, it sends a signal to the primary fuelcontroller 374 along two of the wires in the wire bundle 376. Thissignal causes the primary fuel controller 374 to energize yet anotherspring loaded normally closed solenoid fuel valve 400 by means of thewire pair 406 which causes the spring loaded normally closed solenoidfuel valve 400 to open thereby further increasing the fuel flow to theburner 298. Conversely, if the power level decreases to the range belowwhich the burner is operating, the system closes excess spring loadednormally closed solenoid fuel valves until the number of open valves andthe load are matched.

Under normal operating conditions the output voltage controller 424connect to the primary controller 372 by means of wire 426 and thevoltage controller connects the wire pairs 410, 412 and 414 fromgenerator coils 320, 322 and 324 in parallel and the output frequency ofthe generator is equal to the displacer frequency. If an overload occursas sensed by current sensor 416, the voltage controller preferablydisconnects the load 408 thereby protecting the generator. In the casewhere the output from the generator is being rectified, the frequency ofoperation of the displacer will also be varied so as to optimizeefficiency of the system.

Accordingly, for example, a feedback member comprises controller 372operatively connected to variable fuel flow valve 294 and current sensor416 connected to the output (load 408) whereby the current sensor sensesthe current drawn from the output and the controller adjusts the flowrate of fuel supplied to the combustion chamber based on the amount ofcurrent drawn from the load.

Regenerator

In accordance with another aspect of this invention, a novelconstruction for a regenerator is provided. As shown in FIG. 6a,regenerator 42 is preferably also of a thin wall construction. Inparticular, regenerator 42 may be manufactured from copper (which may becoated with an inverting layer such as silicon monoxide and/or silicondioxide), aluminum (which is coated with an inverting layer such assilicon monoxide and/or silicon dioxide), stainless steel or a supernickel alloy and have a thickness from about 0.0005 to about 0.005inches, more preferably from about 0.001 to about 0.002 inches.

As shown in FIG. 6a, regenerator 42 may comprise a one and preferably aplurality of sections 208 which are joined together by a plurality oflongitudinally extending members 210. Longitudinally extending members210 are spaced apart on opposed sides of openings 212. Openings 212define thermal breaks between sections 208 so as to minimize the heatconducted from hot end 214 to cool end 216. Accordingly, longitudinallyextending members 210 are preferably as thin as possible in thecircumferential direction so as to minimize the heat transferred betweensections 208 while still maintaining sufficient structural integrity ofregenerator 42 so that regenerator 42 may be handled as a single member.In the embodiment of FIG. 1, regenerator 42 comprises a plurality ofindividual sections 208.

Regenerator 42 may be made from sheet metal which is roll formed. Thenlouvres (directing members) 218 and openings 212 are preferably formed(eg. by stamping). Subsequently, the material is formed into acylindrical tube and may be spot welded together to form regenerator 42.Sublouvres (secondary directing members) may be provided as are shown inFIGS. 17, 18 a and 18 b. Regenerator 42 is positioned in fluid flow path40 between outer and inner walls 12 and, 30 as exemplified in FIG. 2a,the regenerator preferably extends along a substantial portion of fluidflow path 40. As shown in FIG. 2a, regenerator 42 commences at about thetop 136 of displacer 46 when displacer 46 is positioned distal to driver48. Further, regenerator 42 preferably ends adjacent opening 158 ininner wall 30.

In order to improve the heat transfer between the working fluid andregenerator 42, regenerator 42 may have a plurality of louvres 218provided therein. Exemplary louvres 218 are shown in more detail in FIG.6d. Regenerator 42 comprises a main body portion 248. Louvres may beformed such as by stamping or other means known in the art. As shown inFIG. 6d, each louvres 218 comprises an angled panel which extendsoutwardly from main body portion 248 and has opposed flanges 250extending between front portion 256 of angled panel 252 and main bodyportion 248. As shown in FIG. 6d, some of the louvres may have angledpanels that extend in a first direction (e.g. upwards in FIG. 6d) andanother set of louvres may extend in the opposite direction (e.g.downwards as shown in FIG. 6d). The designs which are shown in FIGS.12d, 17, 18 a and 18 b may be used for louvres 218.

In FIGS. 6b and 6 c, a heat exchanger using a coil of the material usedto form regenerator 42 of FIG. 6a is shown. Regenerator is preferablyfixed in position such as by spot welding regenerator 42 to one of outerand inner walls 12 and 30. Referring to FIG. 6c, arrows represent theflow of fluid through louvres 218. Louvres 218 direct the fluid to passfirst from one side of main body portion 248 to the opposed side and,subsequently, a portion to flow from the opposed side back to theinitial side of main body portion 248. The continual flow of fluidthrough main body portion 248 (from one side to the other) produces animproved heat transfer between the working fluid and regenerator 42. Inparticular, when the working fluid is passing through the regeneratorfrom heating chamber 140 to cooling chamber 160, regenerator 42accumulates heat which is transferred back to the working fluid when theworking fluid travels from cooling chamber 160 to heating chamber 140.

It is to be appreciated that louvred fins may be used in place of partor all of regenerator 42. Further, a section 208 of the regeneratormaterial may be used as a heat exchanger in passageway 64 or in theupper portion of passageway 40 provided that positioning members areprovided to dimensionally stabilize the upper end of inner and outerwalls 30 and 12. For example, one or more rings 476 may be providedadjacent the upper end of inner wall 30.

Heat exchanger 258 may also be incorporated into the portion of fluidflow path 40 which is positioned in heating zone 22. This is shown inparticular in FIG. 2a . This heat exchanger assists in transferring heatfrom the exhaust gases in first pass 86 of heat exchanger 67 to theworking fluid as it travels from heating chamber 140 to cooling chamber160.

Heat exchanger 258 may be made from the same material as regenerator 42.This is shown in particular in FIG. 6a. In FIG. 6b, a heat exchanger 258is shown comprising a plurality of layers of the louvres material shownin FIG. 6a. The number of layers of louvred main body portion 248 whichis utilized as regenerator 42 or as heat exchanger 258 may varydepending upon the desired thermal efficiency of heat exchanger 258 aswell as regenerator 42. For example, if the radial thickness of fluidflow path 40 is about 0.05 inches, then only a single layer heatexchanger 258 may be required as is shown in FIG. 6a.

Fins

In accordance with another aspect of this invention, there is provided anovel construction for heat exchangers. As discussed above, means toassist in transferring heat between the structural components of theheat engine and a fluid may be provided in any of the air flow passagesof the heat exchanger. For example, they may be provided in passages 64,40, 86, 88 and 102. At least one heat exchange member or fin ispreferably provided in each fluid flow passage. In one embodiment, asexemplified by FIG. 14, the fins are constructed to allow the flow offluid through the fin as the fluid flows axially through the heatexchanger. In another embodiment, the fins are constructed and arrangedto produce a directed fluid flow as the fluid passes through the heatexchanger (e.g. see FIGS. 12, 12 a, 13 and 16). A plurality ofindividual annular fins may be provided. Alternately, one or morecontinuous helical fins as shown in FIG. 16 may be provided. In eithercase, the fins define a plurality of rows of fins in the heat exchangerthat the fluid encounters as it flows through the heat exchanger andthus the fluid is acted on by the fins several times as it flows throughthe heat exchanger. In a further embodiment, the fins are preferablyprovided with directing members whereby the fin is configured andarranges to produce a main flow of fluid which flows through the fin andto produce a secondary fluid flow which passes through the maindirecting members whereby the transfer of heat between the fluid and theheat exchanger is enhanced. Examples of such directing members are shownin FIGS. 16, 17, 18 a and 18 b. The directing members may be configuredand arranged to produce a cyclonic or swirling flow of air (see FIG.12e) or a cross-flow pattern (see FIG. 12f).

In the preferred embodiment of the heat exchanger, as exemplified byFIG. 1, the fins are positioned between two concentric cylinders whichare spaced apart to define an air flow passage. A second air flowpassage is positioned interior of the inner of the two concentriccylinders or exterior of the outer of the two concentric cylinders. Thefins may be affixed to the wall of the heat exchanger by any means knownin the heat exchanger art but are preferably mechanically affixed to oneor both of the inner wall and the outer wall and extend all the wayacross the air flow passage. However, the instant fin design may be usedin a passage of any particular configuration for a heat exchanger. Forexample, the heat exchanger could have a square cross-section defining afirst fluid flow passage with the fins longitudinally spaced apart inthe passage. A plurality of generally parallel tubes (for containing afluid at a second temperature) could extend longitudinally through thefins to thereby define a heat exchanger with a square crosssection.

Referring to FIG. 12, annular fin 428 has a top surface 430 and inneredge 432, an outer edge 434 and a lower surface 436. Top and bottomsurfaces 430 and 436 are opposed surfaces of fin 428. Inner and outeredges 432 and 434 are curved and have a portion which abuts against thelongitudinally extending surface of a wall. See for example surface 438of FIG. 12b. Such rings may be used in a fluid flow passage which existsbetween spaced apart cylindrical tubes. For example, such rings may beinserted in passageways 64 or 102 (see FIG. 1). In order to provide aplurality of annular fins 428 in passageway 102, outer burner shield 70could be placed inside air preheat shield 72 to define passageway 102.Any desired number of rings, preferably a plurality thereof, could beinserted into passageway 102 one at a time with edges 432 and 434pointing towards entry port 104. Rings would then slide along the innerwalls of shields 70 and 72 until they were positioned in the desiredlocation. Annular fins 428 are preferably sized such that edges 432 and434 are drawn towards each other upon insertion into passageway 102. Thepressure between edges 432 and 434 mechanically lock annular fins 428 inposition. Preferably, the pressure which is exerted between fin 428 andshields 70 and 72 is sufficient to ensure that the rate of heat transferbetween shields 70 and 72 and annular fin 428 is maintained over thenormal operating temperature of shields 70 and 72. In this way, as thedimension of passageway 102 may change under different thermalconditions, sufficient contact will be maintained between the annularfins and the walls of passageway 102 to ensure that the desired rate ofheat transfer is maintained.

Another embodiment of such an annular fin is shown in FIG. 12a. In thisembodiment annular fin 440 has opposed surfaces (i.e. top surface 446and the bottom surface) which is generally flat (so as to be generallytransverse to the longitudinal fluid flow path through the heatexchanger) and an outer edge 444 which is curved as in the case ofannular fin 428 to define a collar. Inner edge 442 is not curved.Examples of such fins are shown in passage 102 of FIG. 1. The outerdiameter of fin 440 is selected such that when inserted into annularpassage 102, the pressure which is exerted between outer edge 444 andinner surface of outer burner shield 72 will deform the collar andlockingly hold annular fin 440 in position. It will be appreciated thata curved edge (or collar) may be provided instead only on the inneredge. For example, referring to the fins shown in passageway 88 of FIG.1, inner edge 442 may be curved so as to have the collar like portion offin 440 of FIG. 12a so as to lockingly engage a wall positioned on theinterior of the ring (in this case, inner burner shield 68). The topsurface of the fin preferably extends horizontally to have a blunt nosededge. In this embodiment, the inner diameter of the annular fin isselected so as to be slightly smaller than inner burner shield 68 so asto lockingly engage inner burner shield 68 when inserted therein.Accordingly, in accordance to one aspect of this invention, fins whichhave air flow passages there through are provided to lockingly engageone or both walls of an annular passage to thereby maintain contact withthe selected walls over the operating temperature of the heat exchanger.The passages may be provided as openings 456 in a fin or by passages 474between blades 472 of a fin (see FIG. 13).

As shown in FIG. 16, one or more helical fins 448 may be providedinstead of a plurality of individual annular fins such as fins 428 or440. Helical fin 448 is shown in FIG. 16 in an embodiment where it ispositioned in the annular passage between outer and inner walls 12 and30. In this embodiment, helical fin 448 has curved inner and outer edges450 and 452 for locking engagement with surfaces 36 and 34 respectively.It will be appreciated that helical fin 448 need have only one curvededge (either inner out outer) so as to lockingly engage only a singlewall 12 or 30.

When used in a heat exchanger, the fins are preferably constructed toallow a fluid to flow there through to enhance the heat transfer betweenthe fluid and the heat exchanger. In the embodiment of FIGS. 12 and 12a,fins 428 and 440 are designed to extend fully across the annular gapbetween and inner and an outer wall. Therefore, fin 428 is provided witha plurality of openings 456. In order to improve the heat transferbetween the fluid and the heat exchanger, comprising fin 428 and thesurface of the walls with which fin 428 is in contact, a plurality ofdirecting members 458 may be provided. As the air travelslongitudinally, in the direction of axis A of FIG. 2a, the airencounters top or bottom surface 430 or 436 of fin 428 and passesthrough openings 456, heat is transferred between fin 428 and the fluidpassing through the heat exchanger.

As shown in FIGS. 12 and 12a, each of the direction members 458 extendsupwardly in the same direction. Accordingly, as fluid travelslongitudinally (or axially) through the heat exchanger, the fluid willbe deflected by directing members 458 to swirl around in a cyclonic typeflow. Accordingly, for example, referring to the embodiment of FIG. 12e,a plurality of fins 428 may be positioned on outer surface 32 of outerwall 12. As fluid travels upwardly through openings 456, directingmembers 458 will cause the air to flow cyclonically around outer wall32.

As exemplified by FIGS. 12c and 12 d, some of the directing members 458extend upwardly from top surface 446 and some extend downwardly. Asshown in FIG. 12c, directing members 458 may extend away from surface446 in the same direction or, alternately, as shown in FIG. 12d, theymay extend towards each other. Preferably, directing members 458 extendtowards each other as shown in FIG. 12d.

Directing members 458 have a distal end 460 spaced circumferentiallyfrom the position where directing member 458 contacts top surface 446.As air travels through opening 456, it travels along the bottom surfaceof directing member 458 until it encounters distal end 460. When thefluid encounters distal end 460, turbulent flow is created. As a resultof the turbulent flow, a portion of the fluid, preferably at least about65%, continues to travel upwardly through the heat exchanger while theremainder of the fluid is caused to travel in a reverse manner throughan adjoining opening 456 to the lower surface of fin 440. Accordingly,directing members 458 cause a portion of the fluid travelling throughthe heat exchanger to pass at least twice, and preferably three times,through a fin 440 as the fluid travels axially through the heatexchanger. For example, as the fluid flows through the heat exchanger, aportion of the fluid which has travelled through a fin 440 from lowersurface 436 to top surface 430 will travel in the reverse direction fromtop surface 430 to lower surface 436. This portion of the fluid may thenbe reentrained in the longitudinal flow of fluid through the heatexchanger and travel again from lower surface 436 to top surface 430 andcontinue on flowing through the heat exchanger to encounter another fin440. This is shown in particular in FIG. 12f. This type of flow whereinthe directing members are configured and arranged to cause a portion ofthe fluid which has passed through the a fin from the first opposed sideto the second opposed side to then pass from the second opposed side tothe first opposed side is referred to as “cross-flow”. This flow isadvantageous as it causes a portion of the fluid to be in contact withfin 440 for a greater period of time thereby increasing the heattransfer between fin 440 and the fluid.

Directing members may be formed in several ways. As shown in FIGS. 12cand 12 d, directing members 458 constitute a flange which may be cut orstamped from surface 446. In such a case, only one edge of directingmember 458 may be in contact with the remainder of the fin. An alternateconstruction of a directing member is shown in FIGS. 17, 18 a and 18 b.In this case, directing member 462 is in contact with the fin over morethan one surface. In particular, as shown in FIGS. 17, 18 a and 18 b,directing member 462 has a transverse or radial side 464 which is incontact with top surface 454 as well as opposed longitudinal edges 466which are in contact with top surface 454. The increased contact surfacebetween directing member 462 and the fin permit a greater amount of heatto be transferred between directing member 462 and the fin thusimproving heat transfer between directing member 462 and the fluidflowing through opening 456. Directing members 462 may be produced by astamping operation. Directing members 462 may be provided on any of thefins described herein.

In an alternate embodiment, the fin may comprise an annular member whichcomprises a radial blade. In particular, as shown in FIG. 13, fin 468may have a hub (which may be a curved inner edge or collar 470) and aplurality of blades 472 which extend outwardly, and preferably radiallyoutwardly, there from (or a hub and a plurality of blades which extendinwardly). Blades 472 are preferably angled with respect to the plane offin 468 so as to direct air to flow in a prescribed pattern through theheat exchanger. The spacing between adjacent blades 472 comprises apassage 474 through which a fluid may flow. It will be appreciated thatblades 472 may be oriented in the same direction (as is the case withdirecting members 458 in FIG. 12), thus causing a swirling flow of thefluid in the heat exchanger as is represented by FIG. 12e. It will beappreciated that some of blades 472 may direct the fluid upwardlywhereas others may direct the fluid downwardly (in the same manner asdirecting members 458 of FIGS. 12c or 12 d) to create a cross-flow asshown by FIG. 12f. It will further be appreciated that, as with fin 440,radial blades 472 preferably extend substantially all and preferably allthe way across the annular space between the concentric cylinders so asto direct as much air as possible to flow through passages 474.

In some circumstances, a limited amount of heat may need to betransferred between the fluid and the fin. In such a case, the fin maybe provided with openings without any directing members. An example ofsuch a fin is shown in FIG. 14. In this case, the fin comprises a ring476 having a plurality of openings (for example circular openings 478)provided in top surface 480. Once again, inner and/or outer edge 482 and484 may be curved as shown in FIG. 14.

In a further preferred embodiment, the directing members are themselvesprovided with directing members so as to cause the fluid to travelthrough the directing member as the fluid passes through the heatexchanger. An example of such a directing member is shown in FIG. 16. Inthis case, directing member 458 is provided with at least one andpreferably a plurality of openings 486 provided therein. For example,referring to FIG. 17, directing member 462 has a plurality of openings486 provided therein. Some of the fluid will travel through openings 486as the fluid travels through openings 456 in the fin. Preferably, asshown in FIGS. 18a and 18 b, the directing member is a main directingmember and has a plurality of secondary directing members 488 orsublouvres provided thereon. It will be appreciated that the secondarydirecting members may use the construction techniques of fins 440 (eg.it may be a flanged or stamped opening) or of fins 468 (eg. it may be apassage through a blade). As in the case with the main directingmembers, a secondary directing member is preferably associated with eachsecondary opening 486. As shown in FIG. 18a, secondary directing members488 may all be oriented in the same direction such that as the fluidflows axially through the fin from lower surface 490 to upper surface492, the fluid passes only once (i.e. unidirectionally) from lower orinner surface 494 of directing member 462 to upper or outer surface 496of directing member 462 (inner surface 494 and outer surface 496 areopposed surfaces). In the alternate embodiment of FIG. 18b , some of thesecondary directing members 488 extend upwardly from upper surface 496and some extend downwardly from lower surface 494. As shown in FIG. 18b,directing members may alternately extend upwardly and downwardly or theymay be in any other random pattern (as is also the case with maindirecting members 458 in the embodiments of FIGS. 12c and 12 d). In thiscase, as the fluid travels axially through the heat exchanger from lowersurface 490 to upper surface 492 of the fin, a portion of the fluid willbe caused to pass at least twice through main directing member 462 dueto turbulent flow created by secondary directing members 488 thuscreating cross flow of fluid similar to that shown in FIG. 12f. It willbe appreciated that openings and preferably openings with associatedsecondary directing members 488 may also be provided on blades 472. Inanother embodiment, blades 472 may be provided as secondary directingmembers.

In accordance with another aspect of this invention, any of these findesigns may be provided on the outer surface of outer wall 12 as shownin FIG. 1 to assist in cooling chamber 160. These fins may define theouter perimeter of the heat engine. Alternately, as shown in FIG. 1, afurther outer cylindrical sleeve 522 may be provided. This may be anextension of air preheat shield 72. Air flow path 524 is an extension ofpreheat air flow path 102 and is used to transfer heat from the coolingchamber to the air for combustion. As shown in FIG. 1, the cooling finsof heat exchanger 330 transfer heat from outer wall 12 to the air forcombustion. A fan is optionally provided for producing forced convectionflow through air flow path 524. The fan may be mounted at any positionto provide this flow. As shown in FIG. 1, the fan is provided adjacentthe entrance to air flow path 524. The fan comprises a motor 526 and afan blade 528 driven by the motor. Preferably, both motor 526 and fanblade 528 are annular. They may be mounted on one or both of the wallsthat define air flow path 524 (i.e., outer wall 12 and/or sleeve 522 inthe embodiment of FIG. 1). If fan 528 is annular, then it may be mountedon an annular fan mount 530 which is drivenly connected to annular motor526.

In accordance with another aspect of this invention, any of these findesigns may be provided on the inner surface 60 of heater cup 44 asshown in FIG. 1 to assist in transferring heat from the combustion gasin combustion chamber 92 to the wall of heater cup 44 (the combustionchamber housing) as exemplified by reference numeral 532 in FIG. 1).

It will be appreciated by those skilled in the art that othermodifications may be made to a heat engine and the flashlight disclosedherein and all of these are within the scope of the following claims.For example, the construction of regenerator 42 and the construction ofthe louvred heat exchanger may be used in any application heat exchangeapplication.

Any heat exchanger construction known in the art may be used with thethin walled design provided herein to provide a heat exchanger meansbetween the hot exhaust gases produced in burner cup 44 and the workingfluid in the heat engine. In order to increase the thermal efficiency ofthe heat engine, the air for combustion may be preheated such as by useof the exhaust gas.

I claim:
 1. An apparatus comprising: (a) a heat engine comprising: (i) acontainer defining a sealed region within which a working fluid iscirculated when the heat engine is in use, the sealed region having aheating chamber and a cooling chamber, the heating and cooling chambersbeing in fluid flow communication via a working fluid passageway; (ii) avariable heat source thermally connected to the heating chamber wherebythe variable heat source provides variable heat levels to the workingfluid; (iii) a displacer movably mounted in the sealed region between afirst position and a second position to define a displacer cycleprofile; (iv) a piston movably mounted in the sealed region between afirst position and a second position to define a piston cycle profile,one of the displacer and the piston has an adjustable drive memberassociated therewith for moving the one of the displacer and the pistonin response to a signal and the other of the displacer and the piston ismovable in the sealed region due to forces applied thereto by theworking fluid; (b) a power output member drivenly connected to thepiston and having an output for supplying work; and, (c) an adjustablesignal generator for modulating the signal provided to the adjustabledrive to adjust the cycle profile of the one of the displacer and thepiston.
 2. The apparatus as claimed in claim 1 wherein the power outputmember comprises an electric generator drivenly connected to the heatengine and having an output for supplying electric power to a load andthe piston comprises a portion of the electric generator and thedisplacer is driven by the adjustable drive member.
 3. The apparatus asclaimed in claim 2 wherein the adjustable signal generator comprises asignal modulator and the piston whereby the movement of the pistongenerates a signal that is sent to the signal modulator.
 4. Theapparatus as claimed in claim 3 wherein the piston includes at least onemagnet and the generator includes at least one coil and the piston ismounted in the heat engine for movement relative to the at least onecoil and the movement of the at least one magnet relative to the atleast one coil produces the signal that is sent to the adjustable signalgenerator.
 5. The apparatus as claimed in claim 1 wherein the poweroutput member comprises an electric generator drivenly connected to theheat engine and having an output for supplying electric power to a loadand the piston moves at a phase angle with respect to the displacer andthe adjustable signal generator modulates the signal provided to theadjustable drive member to also adjust the phase angle.
 6. The apparatusas claimed in claim 1 wherein the heat engine has a thermal efficiencythat varies under varying load conditions and the adjustable signalgenerator is responsive to power demand from the power output member tomodulate the signal sent to the adjustable drive member to maintain thethermal efficiency of the heat engine in a preset range.
 7. Theapparatus as claimed in claim 6 wherein the power output membercomprises an electric generator drivenly connected to the heat engineand having an output for supplying electric power to a load and thepiston comprises a portion of the electric generator and the displaceris driven by the adjustable drive member.
 8. The apparatus as claimed inclaim 7 wherein the adjustable signal generator comprises a signalmodulator and the piston whereby the movement of the piston generates asignal that is sent to the signal modulator.
 9. The apparatus as claimedin claim 8 wherein the piston includes at least one magnet and thegenerator includes at least one coil and the piston is mounted in theheat engine for movement relative to the at least one coil and themovement of the at least one magnet relative to the at least one coilproduces the signal that is sent to the signal modulator.
 10. Theapparatus as claimed in claim 1 wherein the displacer moves between afirst position adjacent the variable heat source and a second positiondistal to the variable heat source and has a dwell time in each of thefirst and second positions, and the cycle profile describes the velocityof the displacer as it moves between the first and second positions andthe dwell time of the displacer when it is in each of the first andsecond positions, and the adjustable signal generator modulates thesignal provided to the adjustable drive member to adjust at least one ofthe velocity of the displacer, the dwell time of the displacer when inthe first position and the dwell time of the displacer when in thesecond position.
 11. The apparatus as claimed in claim 10 wherein theheat engine has a thermal efficiency that varies under varying loadconditions and the adjustable signal generator is responsive to powerdemand from the power output member to modulate the signal sent to theadjustable drive member to maintain the thermal efficiency of the heatengine in a preset range.
 12. The apparatus as claimed in claim 11wherein the power output member comprises an electric generator drivenlyconnected to the heat engine and having an output for supplying electricpower to a load and the piston comprises a portion of the electricgenerator and the displacer is driven by the adjustable drive member.13. The apparatus as claimed in claim 12 wherein the adjustable signalgenerator comprises a signal modulator and the piston whereby themovement of the piston generates a signal that is sent to the signalmodulator.
 14. The apparatus as claimed in claim 13 wherein the pistonincludes at least one magnet and the generator includes at least onecoil and the piston is mounted in the heat engine for movement relativeto the at least one coil and the movement of the at least one magnetrelative to the at least one coil produces the signal that is sent tothe signal modulator.
 15. The apparatus as claimed in claim 1 whereinthe sealed region has a cooling chamber for the working fluid and thepiston moves between a first position wherein it is positioned in thecooling region and a second position wherein it is positioned out of thecooling chamber and has a dwell time in each of the first and secondpositions, and the cycle profile describes the velocity of the piston asit moves between the first and second positions and the dwell time ofthe piston when it is in each of the first and second positions, and theadjustable signal generator modulates the signal provided to theadjustable drive member to adjust at least one of the velocity of thepiston, the dwell time of the piston when in the first position and thedwell time of the piston when in the second position.
 16. The apparatusas claimed in claim 15 wherein the heat engine has a thermal efficiencythat varies under varying load conditions and the adjustable signalgenerator is responsive to power demand from the power output member tomodulate the signal sent to the adjustable drive member to maintain thethermal efficiency of the heat engine in a preset range.
 17. Theapparatus as claimed in claim 16 wherein the power output membercomprises an electric generator drivenly connected to the heat engineand having an output for supplying electric power to a load and thepiston comprises a portion of the electric generator and the displaceris driven by the adjustable drive member.
 18. The apparatus as claimedin claim 17 wherein the adjustable signal generator comprises a signalmodulator and the piston whereby the movement of the piston generates asignal that is sent to the signal modulator.
 19. The apparatus asclaimed in claim 18 wherein the piston includes at least one magnet andthe generator includes at least one coil and the piston is mounted inthe heat engine for movement relative to the at least one coil and themovement of the at least one magnet relative to the at least one coilproduces the signal that is sent to the signal modulator.
 20. Theapparatus as claimed in claim 1 wherein the adjustable signal generatorhas a manual adjustment control.
 21. The apparatus as claimed in claim 1wherein the heat engine has a thermal efficiency that varies undervarying load conditions and the adjustable signal generator isresponsive to power demand from the power output member to modulate thesignal sent to the adjustable drive member to maintain the thermalefficiency of the heat engine in a preset range.
 22. The apparatus asclaimed in claim 1 wherein the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load and the heat engine has a thermalefficiency that varies under varying load conditions and the adjustablesignal generator is responsive to power demand from the output tomodulate the signal sent to the adjustable drive member to maintain thethermal efficiency of the heat engine in a preset range.
 23. Theapparatus as claimed in claim 22 wherein the piston comprises a portionof the electric generator and the displacer is driven by the adjustabledrive member.
 24. The apparatus as claimed in claim 23 wherein theadjustable signal generator comprises a signal modulator and the pistonwhereby the movement of the piston generates a signal that is sent tothe signal modulator.
 25. The apparatus as claimed in claim 24 whereinthe piston includes at least one magnet and the generator includes atleast one coil and the piston is mounted in the heat engine for movementrelative to the at least one coil and the movement of the at least onemagnet relative to the at least one coil produces the signal that issent to the signal modulator.
 26. The apparatus as claimed in claim 1wherein the power output member comprises an electric generator drivenlyconnected to the heat engine and having an output for supplying electricpower to a load and the piston comprises a portion of the electricgenerator.
 27. The apparatus as claimed in claim 26 wherein theadjustable signal generator comprises a signal modulator and the pistonwhereby the movement of the piston generates a signal that is sent tothe signal modulator.
 28. The apparatus as claimed in claim 27 whereinthe piston includes at least one magnet and the generator includes atleast one coil and the piston is mounted in the heat engine for movementrelative to the at least one coil and the movement of the at least onemagnet relative to the at least one coil produces the signal that issent to the signal modulator.
 29. The apparatus as claimed in claim 1wherein the power output member comprises an electric generator drivenlyconnected to the heat engine and having an output for supplying electricpower to a load and the apparatus further comprises a feedback memberresponsive to power demand from the electric generator by the load tomodulate the amount of heat provided by the heat source to the workingfluid.
 30. The apparatus as claimed in claim 29 wherein the feedbackmember includes a thermal sensor thermally connected to a thermal sourcewhose temperature changes as the power demand from the output varies.31. The apparatus as claimed in claim 30 wherein the thermal sensor isreconfigurable on heating and is mechanically connected to the variableheat source to adjust the amount of heat provided by the variable heatsource in response to a reconfiguration of the thermal sensor.
 32. Theapparatus as claimed in claim 31 wherein the thermal source is the heatsource whereby the temperature of the heat source is used to sense thepower demand applied to the output.
 33. The apparatus as claimed inclaim 32 wherein the feedback member further comprises an internal loadmember which draws current from the output.
 34. The apparatus as claimedin claim 30 wherein the feedback member comprises a circuit including aresistor electrically connected to the circuit to draw currentproportional to the power demand drawn from the output and the thermalsource is the resistor whereby the temperature of the resistor is usedto sense the power demand from the output.
 35. The apparatus as claimedin claim 1 wherein the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source has acontrol member to adjust the temperature of the variable heat source anda feedback member is drivingly connected to the control member andcomprises a circuit including a sensor portion which provides a signalto the control member based on the power demand drawn from the output.36. The apparatus as claimed in claim 35 wherein the sensor portionprovides an electrical signal to the control member causing the variableheat source to adjust the amount of heat provided to the working fluidin response to the signal from the sensor portion.
 37. The apparatus asclaimed in claim 1 wherein the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member is drivingly connected to the variable fuel flow valveand includes a thermal sensor thermally connected to the combustionchamber whereby the temperature of the combustion chamber variesinversely to the power drawn from the linear generator by the load, thethermal sensor senses the temperature of the combustion chamber and thefeedback member adjusts the flow rate of fuel supplied to the combustionchamber to maintain the temperature of the combustion chamber within apreset range.
 38. The apparatus as claimed in claim 1 wherein the poweroutput member comprises an electric generator drivenly connected to theheat engine and having an output for supplying electric power to a load,the variable heat source comprises a combustion chamber and a variablefuel flow valve associated thereto, the variable fuel flow valve isadjustable to a plurality of positions to provide varying flow rates offuel to the combustion chamber, a feedback member is drivingly connectedto the variable fuel flow valve and comprises a circuit including aresistor electrically connected to the circuit to draw currentproportional to the power demand drawn from the output, and a thermalsensor thermally connected to the resistor whereby the thermal sensorindirectly senses the power demand of a load applied to the output andthe feedback member adjusts the flow rate of fuel supplied to thecombustion chamber to maintain the temperature of the combustion chamberwithin a preset range.
 39. The apparatus as claimed in claim 1 whereinthe power output member comprises an electric generator drivenlyconnected to the heat engine and having an output for supplying electricpower to a load, the variable heat source comprises a combustion chamberand a variable fuel flow valve associated thereto, the variable fuelflow valve is adjustable to a plurality of positions to provide varyingflow rates of fuel to the combustion chamber, a feedback member isdrivingly connected to the variable fuel flow valve and comprises acircuit including an internal load member which draws current from theoutput and a resistor electrically connected to the circuit to drawcurrent relative to the power demand drawn from the output, and athermal sensor is thermally connected to the resistor whereby thethermal sensor indirectly senses the power demand of the load and theinternal load and the feedback member adjusts the flow rate of fuelsupplied to the combustion chamber to maintain the temperature of thecombustion chamber within a preset range.
 40. The apparatus as claimedin claim 1 wherein the power output member comprises an electricgenerator drivenly connected to the heat engine and having an output forsupplying electric power to a load, the variable heat source comprises acombustion chamber and a variable fuel flow valve associated thereto,the variable fuel flow valve is adjustable to a plurality of positionsto provide varying flow rates of fuel to the combustion chamber, afeedback member comprises a controller operatively connected to thevariable fuel flow valve and a current sensor connected to the outputwhereby the current sensor senses the current drawn from the output andthe controller adjusts the flow rate of fuel supplied to the combustionchamber based on the amount of current drawn from the load.
 41. Theapparatus as claimed in claim 40 wherein the variable fuel flow valvecomprises a plurality of valves each of which is independently operableby the controller.
 42. The apparatus as claimed in claim 1 wherein thepower output member comprises a linear to rotary converter.